Practical guides for better decisions.

How many days are in each month and how does the leap year rule work?

Short answer: seven months have 31 days and four have 30 and February has 28 or 29. A year is a leap year if divisible by 4 except century years not divisible by 400. Full reference tables.

Hourly wage to annual salary table: what $15 to $75 an hour pays per year

Short answer: $22 an hour at 40 hours a week for 52 weeks is $45,760 a year (2,080 hours). Tables for common hourly rates and schedules plus salary to hourly equivalents.

How a Mathify Calculation Is Built and Tested

A plain-English look at how a Mathify calculator goes from formula to result: pure functions and input checks and known-answer tests.

Mortgage payment on $300,000 at 6.5% for 30 years: how much per month?

Short answer: a $300,000 loan at 6.5% over 30 years costs $1,896.20 a month in principal and interest. Here is the full payment table per $100,000 borrowed across common rates and terms.

How to Connect Mathify Calculators to an AI Assistant (MCP)

Add Mathify as a remote MCP server so your AI assistant can search and run calculators instead of guessing. Generic steps and what each tool does.

How to Embed a Mathify Calculator on Your Website

Add a working Mathify calculator to your own page with one iframe. Includes the address format and a copy-ready snippet and a few things to check.

Math and Money Glossary: Plain Definitions With a Calculator for Each

Short answer: a glossary of the percentage, statistics, interest, loan, business, health and date terms people search for most, each defined in one precise sentence and linked to the Mathify calculator that works it out.

Mathify Accuracy and Corrections: What We Do and How to Report an Error

What backs a Mathify result and where its limits are. Also how to report a wrong answer so it can be reproduced and fixed.

Mathify REST API and OpenAPI: Use Calculators from Scripts and GPT Actions

Call Mathify calculators with a plain POST request and import the OpenAPI file into tools that support it. Includes a tested curl example and the error codes.

Mean vs Median vs Mode: Which Average Should You Use?

Short answer: use the mean when values are fairly even, the median when a few extreme values would drag the average, and the mode for the most common category. Worked examples show when each one misleads.

Percent vs Percentage Points: What Is the Difference?

Short answer: a percentage point is the plain subtraction of two percentages, while percent change is that gap divided by the starting value. A rate moving from 4% to 5% is up 1 percentage point and up 25 percent.

Percentage cheat sheet: tip amounts and fraction to decimal to percent

Short answer: a 20% tip on an $85 bill is $17.00 and 3/8 is 0.375 or 37.5%. Tip tables for common bills and a fraction to decimal to percent chart.

Pounds, Kilograms and Gallons: Unit Mix-Ups That Change Your Answer

Short answer: 1 lb is exactly 0.45359237 kg, a US gallon is 3.785411784 L and a UK gallon is 4.54609 L, about 20% bigger. Using the wrong factor or the wrong gallon changes results by far more than rounding.

How accurate is the Rule of 72: exact doubling time vs 72 divided by the rate

Short answer: the Rule of 72 is within about 1% of the exact doubling time from 6% to 10%, within 2% from 4% to 12%, and drifts further at high rates. Full accuracy table for 1% to 50%.

How to Share a Prefilled Mathify Calculation with a Link

Add the numbers to the address and the calculator opens already filled in. How the mf_ parameters work and which pages support them.

Simple vs Compound Interest and APR vs APY Explained With Numbers

Short answer: simple interest earns on the original amount only, compound interest earns on interest too, and APY is the APR after compounding is counted. On 10,000 at 5% for 10 years that is 15,000 simple against 16,470.09 compounded monthly.

What does $1,000 grow to: annual vs monthly compounding by rate and years

Short answer: at 6% for 10 years $1,000 grows to $1,790.85 with annual compounding and $1,819.40 with monthly compounding. Full tables for 2% to 10% over 5 to 30 years.

What Is WebMCP and How Does Mathify Use It?

WebMCP is an early browser proposal that lets a web page offer tools to an AI agent. Here is what it is and what Mathify registers on its pages.

Why AI Chatbots Get Math Wrong and How a Calculator Tool Fixes It

AI assistants write text that looks right and can still miscalculate. Connecting a calculator tool lets the assistant hand the arithmetic to code instead.

Why Does 0.1 + 0.2 Not Equal 0.3 (and How to Split a Bill Without Losing a Cent)

Short answer: computers store most decimals as binary approximations, so 0.1 + 0.2 comes out as 0.30000000000000004. Money should be handled in whole cents, which is also how to split a bill so the shares add up exactly.

Why Two Date and Age Calculators Give Different Answers (Daylight Saving and Month Ends)

Short answer: date tools disagree because of daylight saving shifts, month-end rules, and whether the end date is counted. Worked examples show each case, and we explain the daylight saving bug we fixed in our own date calculators.

AI Calculator Guide — Solve Math & Finance Problems Naturally

Age Calculator: Exact Age & Time Difference Calculation Guide

Calculate your exact age in years,months,days,hours,and minutes,or compute the time difference between two dates.

Base64 Encoder/Decoder: Practical Guide to Data Serialization

Learn how Base64 encoding works,its binary-to-text translation rules,and common development use cases.

Developer Utilities: Base64 Encoding, Text Case, & Case Cleaning Guide

Learn the mechanics of Base64 encoding/decoding and how text cleaning tools speed up programming workflows.

BMI Calculator: Complete Body Mass Index & Health Status Guide

Learn how Body Mass Index (BMI) is calculated,its classifications,and its relationship to overall wellness.

Brick Calculator: Estimating Bricks, Mortar & Material Quantities

Estimate the number of bricks and volume of mortar needed for masonry wall construction.

CAGR Calculator: Understanding Compound Annual Growth Rate

Calculate the annualized return of an investment over time using the CAGR formula.

Calorie Calculator: Daily Calorie Intake & BMR Estimation Guide

Calculate your daily calorie requirements for weight loss,maintenance,or muscle gain using BMR and TDEE.

Calorie Deficit & TDEE: The Ultimate Macro Planning Guide

Learn the science of calorie deficits,calculate your TDEE,and split macronutrients for body composition goals.

Carbon Footprint: Measuring & Reducing Your Greenhouse Gas Emissions

Calculate your annual carbon emissions from transport,utilities,and consumption,and explore reduction plans.

College Planning 2026: GPA Optimization & Student Loan Payback Methods

Track and optimize your cumulative GPA while calculating student loan payoff structures to save on interest.

Compound Interest Calculator: In‑Depth Guide to Exponential Growth

Learn the mathematics of compound interest and how regular contributions accelerate wealth building.

EV vs Hybrid Car Cost Calculator: 2026 Purchase & Fuel Savings Guide

Compare purchase premium,tax rebates,charging costs,and hybrid fuel efficiency to calculate real vehicle ROI.

FD Calculator: Fixed Deposit & Certificate of Deposit (CD) Maturity Guide

Calculate the maturity value and interest earnings of fixed deposits (FD) and certificates of deposit (CD).

Freelance Rate Calculator: Pricing Guide for Setting Hourly Rates

Calculate the hourly or project rate you need to charge as a freelancer to cover salaries,taxes,and expenses.

Freelancer Guide 2026: Tax Deductions & Distraction Cost Management

Optimize your freelance profits by identifying deductible expenses and calculating the financial cost of distractions.

GPA Calculator: Academic Success & Grade Point Average Guide

Understand how to calculate your semester and cumulative GPA using weighted and unweighted grade scales.

VAT & Sales Tax Calculator: Inclusive vs Exclusive Tax Pricing

Calculate sales tax or value-added tax (VAT) totals and determine pre-tax pricing.

HISA & Compound Interest: 2026 Wealth-Building Strategies

Maximize your cash savings in 2026 by leveraging high-interest savings accounts (HISA) and monthly compounding.

Home Affordability Guide: How Much House Can You Afford?

Analyze your home buying budget using the 28/36 debt-to-income rule and down payment calculations.

Home Remodeling Estimating: Material & Cost Calculations for 2026

Estimate materials and project costs for home remodeling,from square footage of rooms to paint and concrete volumes.

Ideal Weight Calculator: Finding Your Healthy Target Range

Discover your ideal body weight range based on Devine,Robinson,Miller,and Hamwi formulas.

How to Adjust for Inflation: Protecting Cash Flow & Buying Power in 2026

Calculate how inflation erodes your cash value and learn how to adjust contracts,salaries,and budgets for inflation.

Loan Amortization: Schedule Calculations & Payment Structures

Understand how monthly loan payments are divided between principal and interest using amortization schedules.

Margin Trading Calculator: Leveraging Trades & Risk Management

Understand margin requirements,leverage multipliers,and maintenance margin call prices.

Mortgage Amortization Guide: Payoff Acceleration & Refinance Break-Even

Analyze how extra principal payments shorten your home loan,and calculate the break-even point for refinancing in 2026.

Mortgage Calculator: The Ultimate Home Loan & P&I Payment Guide

Calculate your monthly mortgage payments including principal,interest,taxes,and home insurance costs.

Mutual Funds & Step-Up SIP: The Compound Wealth Blueprint for 2026

Boost your long-term investment returns by increasing your monthly SIP contributions annually. Compare with CAGR.

Ohm's Law Calculator: Voltage, Current, Resistance & Power Guide

Master Ohm's Law formulas to calculate voltage,current,resistance,and electrical power with worked examples.

Ovulation Tracker: Complete Guide to Fertility & Conception Windows

Estimate your fertile window and next ovulation date using cycle length calculations and biological markers.

Password Generator: How to Create Strong & Secure Passwords

Learn the mathematics of password entropy and how to generate highly secure,random passwords.

Percentage Calculator: Methods, Formulas & Practical Examples

Master percentage calculations,including percent change,percentage of,and percentage increase or decrease.

Pregnancy Due Date Calculator: Methods for Estimating Your Due Date

Calculate your estimated due date using Naegele's rule,Mittendorf-Williams methods,or ultrasound markers.

RD Calculator: Recurring Deposit Interest & Maturity Calculation Guide

Estimate the interest earned and final payout on recurring deposits (RD) with fixed monthly savings.

Rental Yield & Cash-on-Cash Return: Real Estate ROI Modeling

Learn how to analyze rental properties like a pro using gross yield,net yield,and cash-on-cash return calculations.

Rent vs Buy: Financial Analysis of Homeownership vs Renting

Compare the long-term total cost of buying a home versus renting and investing the difference.

SaaS Unit Economics: Master Churn, MRR, & CAC Payback in 2026

Understand the core growth metrics for software subscriptions: MRR growth, LTV:CAC ratios, and customer churn calculation.

Self-Employment Tax Calculator: 1099 Freelance Tax Estimate Guide

Estimate your Social Security and Medicare taxes for 1099 freelance or contract business income.

SIP Calculator: Complete Guide to Systematic Investment Plans

Calculate the future value of your mutual fund investments using standard Systematic Investment Plan (SIP) math.

Circadian Productivity: Sleep Cycle Timing & Focus Time Audits

Optimize your energy levels by aligning your sleep with natural REM cycles and performing daily focus time audits.

Sleep Cycles & Productivity: Wake Up Refreshed & Optimize Rest

Master your circadian rhythm by planning bedtimes and wake-up times around 90-minute sleep cycles.

Solar Panel ROI: Payback Period & Energy Savings Calculation Guide

Calculate the return on investment (ROI) and payback period of residential solar panel installations.

Solar Panel ROI 2026: Payback Period & Energy Savings Forecast

Forecast your solar investment payback period,net metering credits,and long-term energy bill savings.

Startup Runway: Calculating Cash Burn Rate & Survival Period

Determine your startup's monthly burn rate and survival runway to manage venture cash flow.

Step-Up SIP Calculator: Boosting Returns with Annual Increments

Learn how increasing your monthly SIP contributions annually can multiply your long-term wealth.

SWP Calculator: Systematic Withdrawal Plans & Retirement Income Guide

Model your retirement cash flow and calculate portfolio longevity using Systematic Withdrawal Plan (SWP) math.

Tile Calculator: Flooring & Wall Material Layout Estimates

Calculate tiles,grout,and boxes needed for residential flooring or wall renovation.

The Etiquette of Splitting: Tip Splits & Group Bill Cost Sharing

Master the social rules of dividing dining bills,calculating appropriate tips,and splitting group expenses.

Velocity Calculator: Calculating Speed, Distance, Time & Acceleration

Understand the physics of velocity,average speed,and acceleration with standard equations and calculation examples.

Water Intake Calculator: Daily Hydration Requirements & Benefits

Calculate how much water you should drink daily based on weight,activity level,and environmental climate.

XIRR Calculator: Annualized Return for Irregular Cash Flows Explained

Learn how to calculate XIRR for investments with uneven buy-and-sell cash flows.

Body Fat Calculator: Navy Method Guide to Composition Insights

Learn how the Navy body fat method works,how to measure correctly,and how to interpret your results with practical examples and improvement tips.

Heart Rate Zones Calculator: Training Guide for Smarter Workouts

Understand heart rate zones,how to calculate them,and how to structure workouts for fat loss,endurance,and performance gains.

Macro Calculator: High-Protein Meal Planning Guide

Master macronutrient ratios for fat loss,muscle gain,or maintenance. Includes macro splits,meal planning tips,and calculator-driven examples.

Mortgage Calculator: First-Time Homebuyer Guide

Understand mortgage types,down payment strategies,and monthly payment breakdowns with our calculator-driven walkthrough for first-time buyers.

Complete Car Ownership Cost Calculator Guide: Purchase, Financing, Insurance, Maintenance & Total Cost Analysis

Comprehensive guide to calculating true car ownership costs. Master purchase price,auto loans,insurance,fuel,maintenance,depreciation,and total cost of ownership for smart vehicle financial decisions.

Complete Fitness Calculator Guide: BMI, Calories, Macros, Body Fat & Workout Planning for 2025

Comprehensive 10,000+ word guide covering all fitness calculations: BMI, calorie needs (TDEE), macro distribution, body fat percentage, ideal weight, one-rep max, heart rate zones, and progressive overload planning. Science-based formulas with real examples.

Complete Unit Conversion Guide: Master Length, Weight, Temperature & Volume Calculations

Comprehensive guide to unit conversions with practical examples,formulas,and calculator strategies. Learn metric to imperial conversions,temperature scales,volume measurements,and more for everyday and professional use.

Complete Date & Time Calculator Guide: Duration, Age, Deadlines, Business Days & Time Math

Master date and time calculations with practical examples and formulas. Learn to calculate durations,ages,deadlines,business days,time zones,and project timelines for personal and professional planning.

Complete Home Renovation Calculator Guide: Budgeting, Costs, ROI & Project Planning for Remodeling

Master home renovation costs and budgeting with comprehensive calculations. Learn to estimate materials,labor,ROI,financing options,and project planning for kitchen,bathroom,and whole-house remodels.

How to Save Money Fast: 15 Practical Calculator-Based Strategies That Actually Work

Discover proven money-saving strategies with step-by-step calculator guides. Learn how to save $10,000 in a year,reduce expenses by 30%,and build wealth faster using data-driven financial planning tools.

Investment Calculator Guide: SIP, Mutual Funds, Stocks & Portfolio Growth Strategies for 2025

Complete guide to investment calculations including SIP,lumpsum,mutual funds,stock returns,dividend yield,portfolio rebalancing,and retirement corpus planning. Learn to calculate returns,compare investment options,and build wealth systematically.

Mortgage & Home Buying Calculator Guide: Affordability, Payments, Refinancing & Real Estate Math for 2025

Complete 8,000+ word guide to mortgage calculations,home affordability,monthly payments,refinancing analysis,rent vs buy decisions,and real estate investment math. Includes amortization schedules,PMI calculations,and tax deduction strategies.

Personal Finance 101: Complete Guide to Managing Money, Budgeting, and Building Wealth in 2025

Master personal finance with this comprehensive 10,000+ word guide covering budgeting,debt management,investing,retirement planning,and wealth-building strategies. Includes calculator tools,real examples,and actionable steps for financial success.

SaaS Metrics Calculator Guide: MRR, ARR, Churn, LTV, CAC & Essential Financial KPIs

Complete guide to SaaS metrics and calculations. Master MRR,ARR,churn rate,customer lifetime value,CAC,and critical KPIs for subscription business growth and investor reporting.

EV vs Gas Car Cost Calculator: Which is Cheaper in the Long Run?

Brokerage Calculator: Calculate Trading Costs and Profit Margins

Learn how to calculate brokerage fees,trading costs,and profit margins for stock investments. Understand how commissions impact your returns and use our brokerage calculator to make informed trading decisions.

Car Loan Calculator: Complete Guide to Auto Financing

Learn how to calculate car loan payments,compare auto loan offers,understand interest rates,and make informed vehicle financing decisions with our comprehensive guide.

Concrete Calculator: How to Calculate Concrete Needed for Your Project

Learn how to calculate concrete volume for slabs,footings,columns,and more. Understand concrete mix ratios,ordering tips,and use our concrete calculator for accurate estimates.

Daily Compound Interest Calculator: Maximize Your Savings Growth

Learn how daily compound interest works,calculate returns on daily compounding investments,and understand how frequent compounding accelerates your wealth growth compared to monthly or annual compounding.

Fuel Economy Calculator: How to Calculate MPG and Save Money on Gas

Learn how to calculate fuel economy (MPG),compare vehicle efficiency,estimate fuel costs,and use our fuel economy calculator to make smarter vehicle and driving decisions.

Inflation Calculator: Understand How Inflation Affects Your Money Over Time

Learn how to calculate inflation's impact on purchasing power,compare prices across different years,and understand how inflation erodes your savings. Use our inflation calculator to see real value changes.

One Rep Max Calculator: Calculate Your Maximum Strength Safely

Learn how to calculate your one-rep maximum (1RM) safely without testing it directly. Understand different 1RM formulas,training zones,and use our calculator to plan your strength training program.

Paint Calculator: How to Calculate Paint Needed for Your Room

Learn how to calculate how much paint you need for walls,ceilings,and exterior surfaces. Understand coverage rates,paint types,and use our paint calculator for accurate estimates.

Square Footage Calculator: How to Calculate Area for Real Estate and Home Projects

Learn how to calculate square footage for rooms,houses,land,and construction projects. Understand measurement methods,conversions,and use our square footage calculator for accurate area calculations.

Stock Average Calculator: How to Calculate Your Average Stock Price

Learn how to calculate your average stock purchase price when buying shares at different prices. Understand dollar-cost averaging,weighted averages,and portfolio management strategies.

EMI Calculator: How to Calculate Equated Monthly Installments

A complete guide to EMI: the formula, manual method, pitfalls, and worked examples. Learn how lenders compute EMIs and how to optimize your loan.

Unit Converter: A Complete Guide to Accurate Measurement

SI fundamentals,common conversion pitfalls,precision vs rounding,and domain-specific gotchas for length,mass,temperature,volume,and data units.

Tip Calculator & Bill Splitting: Complete Guide to Dining Math

Master tipping etiquette and bill splitting with comprehensive calculations for restaurants,services,and group dining. Learn regional customs,fair splitting methods,and digital payment solutions.

Retirement Calculator: Complete Guide to Planning Your Financial Freedom

Master retirement planning with comprehensive calculations for savings,investments,and income needs. Learn to project retirement funds,optimize contributions,and achieve financial independence.

Loan Comparison Calculator: Make the Best Borrowing Decision

Compare loans effectively using comprehensive calculations for interest rates,fees,and total costs. Learn to evaluate personal loans,mortgages,auto loans,and more.

Discount Calculator: Master Shopping Savings and Retail Math

Learn how to calculate discounts,stack savings,compare deals,and maximize your shopping budget. Complete guide to percentage off,BOGO deals,and sale prices.

Scientific Calculator: Complete Guide to Functions and Usage

Master scientific calculator functions from basic operations to advanced trigonometry,logarithms,and statistics. Learn when and how to use each feature.