Calculators
Percentages, BMI, tip splits, GPA, age, ratios — everyday math the phone calculator can't do neatly.
13 tools · all run in your browser
The calculators most people search for online: BMI (in metric or imperial), percentage-of / percentage-change / add-tax, tip calculator that handles bill splits, GPA that supports 4.0 / 4.3 / 5.0 / percentage grading scales, age in years-months-days as well as total minutes-alive, ratio simplifier, TDEE and ideal body weight for fitness planning.
For finance-specific math (mortgage, loan, ROI, compound interest) see the Finance Calculators category instead. For unit-to-unit conversion (cups to ml, kg to lb) see Unit Converters.
Every result updates as you type. Nothing is submitted anywhere; everything runs on your device.
All calculators
- Age CalculatorEnter a date of birth to see age in years, months, days, hours, minutes, and seconds. Optionally compute age at any past or future date.
- BMI CalculatorCalculate your Body Mass Index (BMI) in metric or imperial units. Shows category and healthy weight range for your height.
- Body Fat Calculator (US Navy)Estimate body fat percentage using the US Navy tape-measure method. Needs only waist, neck (and hip, for women), and height. Metric or imperial.
- Coin FlipperFlip a coin online — one flip, or run up to 10,000 flips to see heads/tails distribution and longest streaks. Uses cryptographic randomness by default.
- Dice RollerRoll dice using D&D-style notation like 3d6, 1d20+5, or 2d10-3. Supports D4 through D100 presets, custom sides, modifiers, and cryptographic randomness.
- Fuel Cost CalculatorCalculate how much fuel a trip will cost. Supports MPG (US and UK), L/100 km, and km/L, with prices per gallon or liter. Great for road-trip budgeting.
- GPA CalculatorCalculate your weighted GPA across any number of courses. Supports 4.0, 4.3, and 5.0 letter-grade scales plus 0-100 percentage.
- Ideal Body Weight CalculatorEstimate ideal body weight (IBW) using the Devine, Robinson, Miller, and Hamwi formulas. Compares all four in metric and imperial, based on height and sex.
- Percentage CalculatorEvery percentage calculation in one place: X% of Y, X is what % of Y, change from A to B, add/subtract %, add tax. Runs entirely in your browser.
- Ratio CalculatorSimplify any ratio a:b to lowest terms, get the decimal / percentage / reciprocal, and solve for a missing side when scaling proportionally.
- TDEE CalculatorCalculate your Total Daily Energy Expenditure (TDEE) — the calories you burn per day. Includes BMR (Mifflin-St Jeor), activity multiplier, and cut / maintain / bulk targets.
- Tip CalculatorCalculate tip amount, total, and per-person split for any bill. Presets for 10 / 15 / 18 / 20 / 25%. Optional round-up to the nearest dollar.
- Unit Price CalculatorEnter multiple products with price and quantity — the calculator ranks them by price per unit (per oz, per lb, per kg, per sheet, whatever) and highlights the best deal.
Frequently asked
Metric: weight (kg) ÷ height (m)². Imperial: (weight in lb × 703) ÷ height (in)². The formula is the same globally — our BMI Calculator handles both unit systems and shows the interpretation category (underweight, normal, overweight, obese) per WHO thresholds.
For adults: 18.5-24.9 is considered "normal." Below 18.5 is underweight, 25-29.9 is overweight, 30+ is obese. BMI is a screening tool, not a diagnosis — it doesn't account for muscle mass, bone density, or fat distribution.
Use our Tip Calculator — enter the bill total, pick a tip percentage, and (optionally) the number of people. Shows the tip amount, the total with tip, and each person's share.
Multiply: 150 × 0.20 = 30. Or use our Percentage Calculator in "% of" mode — it also handles "45 is what percent of 180?" (inverse), "change from A to B", and add-tax/markup.
Total Daily Energy Expenditure — the calories your body burns in a day, including exercise. Our TDEE Calculator uses the Mifflin-St Jeor formula (age, sex, height, weight) times an activity multiplier. Used as a starting point for calorie planning.
Weighted average of grade points across all courses. Per course: grade × credit hours. GPA = total grade points ÷ total credit hours. Our GPA Calculator supports the four common scales (4.0, 4.3, 5.0, percentage).