Free Online Calculators

Fast, accurate, and free — for finance, health, math, and everyday life.

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Finance
Mortgage, loan, compound interest, retirement, tax, ROI and more.
13 calculators
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Health & Fitness
BMI, calories, body fat, BMR, ideal weight, sleep and water intake.
7 calculators
🔢
Math
Scientific calculator, percentage, fractions, averages and area.
6 calculators
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Other
Age, date difference, GPA, grades, hours worked and concrete.
6 calculators
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Conversions
Length, weight, temperature, volume, currency and more.
16 converters
⭐ Most popular
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Mortgage
Monthly payment
⚖️
BMI
Body mass index
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Compound Interest
Investment growth
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Currency
Live exchange rates
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Calorie Needs
Daily TDEE
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Loan
Payment schedule
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Age Calculator
Exact age
%
Percentage
Quick % calc

Why use MostCalculators?

⚡ Instant results
All calculations happen in your browser — no loading, no waiting.
🔒 Private
No data is sent to any server. Your numbers stay on your device.
📱 Mobile friendly
Works perfectly on phones, tablets, and desktops.
🌐 Works offline
Once loaded, all calculators work without internet (except live currency).

All Calculator Categories

💰 Finance Calculators

Calculate mortgage payments, loan amortization, compound interest, retirement savings, US income tax, sales tax, VAT, ROI, commission, inflation, and tip splitting. All free with no sign-up required.

🏃 Health & Fitness Calculators

Calculate BMI (body mass index), daily calorie needs (TDEE), body fat percentage using the Navy method, basal metabolic rate (BMR), ideal body weight, optimal sleep times, and daily water intake.

🔢 Math Calculators

Full scientific calculator with trig and logarithm functions, percentage calculator (3 modes), fraction arithmetic, average (mean, median, mode, range), random number generator, and area of 6 geometric shapes.

🗓️ Everyday Calculators

Calculate your exact age from date of birth, days between two dates, GPA from letter grades and credits, weighted final grades, hours worked with pay, and concrete bags needed for construction projects.

🔄 Unit Converters

Convert length, weight, temperature, volume, speed, area, data storage, pressure, and energy. Plus live currency exchange rates for 32 currencies and cooking unit conversions for kitchen measurements.

💱 Currency Converter

Live exchange rates for USD, EUR, GBP, JPY, CAD, AUD, CHF, CNY, INR, MXN, BRL, KRW, NGN, KES, GHS and 18 more currencies. Rates fetched automatically from open exchange rate API.

Common Conversion Quick Reference

1 mile = 1.60934 km
1 kg = 2.20462 lbs
1 inch = 2.54 cm
1 gallon (US) = 3.78541 L
0°C = 32°F
100°C = 212°F
1 foot = 30.48 cm
1 pound = 453.592 g
1 acre = 4,046.86 m²
1 kWh = 3,600 kJ
1 bar = 14.5038 psi
1 horsepower = 745.7 W
1 stone = 6.35029 kg
1 liter = 33.814 fl oz
1 atm = 101.325 kPa
1 kcal = 4,184 J
1 cup = 236.588 mL
1 yard = 0.9144 m
1 GB = 1,024 MB
1 knot = 1.852 km/h

Frequently Asked Questions

How do I calculate a mortgage payment?

Use the formula M = P[r(1+r)^n]/[(1+r)^n-1], where P is the loan principal, r is the monthly interest rate, and n is the number of payments. Our mortgage calculator also shows a full 12-month amortization table.

How do I calculate BMI?

BMI = weight (kg) ÷ height² (m). For example, 70 kg ÷ (1.75m)² = 22.9. A BMI between 18.5 and 24.9 is considered a healthy weight. Our calculator supports both metric and imperial units.

How do I convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 (or 1.8) then add 32. Example: 100°C × 1.8 + 32 = 212°F. To go the other way, subtract 32 then multiply by 5/9.

How do I calculate compound interest?

A = P(1 + r/n)^(nt), where P is principal, r is the annual rate, n is compounding frequency, and t is time in years. With monthly contributions, the future value is even higher — our calculator accounts for both.

How many calories do I need per day?

Your TDEE (Total Daily Energy Expenditure) depends on age, gender, weight, height, and activity level. We use the Mifflin-St Jeor equation for BMR, then multiply by an activity factor from 1.2 (sedentary) to 1.9 (very active).

How do I calculate ROI?

ROI = (Final Value − Initial Investment) ÷ Initial Investment × 100. For example: invested $10,000, grew to $14,500 → ROI = 45%. Our calculator also shows annualized ROI for multi-year investments.

How do I calculate GPA?

GPA = sum of (grade points × credit hours) ÷ total credit hours. Grade points: A=4.0, B=3.0, C=2.0, D=1.0, F=0. Our GPA calculator lets you enter multiple courses with different credit weights.

Are these calculators free?

Yes — all 37+ calculators on MostCalculators are completely free. No sign-up, no subscription, no hidden fees. All calculations happen instantly in your browser and work offline once loaded.