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Calculator library
Useful answers, without the clutter
Each calculator explains the formula, shows a worked example, and keeps your inputs on your device.
Semester Grade Calculator
Combine assignment categories into a semester grade average.
Open calculatorSimple Interest Calculator
Find simple interest and final balance using principal, annual rate, and time.
Open calculatorSleep Calculator
Find ideal bedtimes or wake times aligned to 90-minute sleep cycles.
Open calculatorSoil Calculator
Estimate topsoil or fill volume for garden and landscaping projects.
Open calculatorSpeed Converter
Convert speed between mph, kph, knots, and meters per second.
Open calculatorSpeedometer Calculator
Correct speedometer error after changing tire diameter.
Open calculatorSquare Footage Calculator
Calculate room or floor area from length and width.
Open calculatorSquare Root Calculator
Find the square root of any non-negative number instantly.
Open calculatorStair Calculator
Calculate rise, run, and tread count for safe stair dimensions.
Open calculatorStandard Deviation Calculator
Measure spread in a data set with standard deviation.
Open calculatorStorage Calculator
Estimate storage needs from file sizes and retention periods.
Open calculatorStudent Loan Calculator
Estimate monthly student loan payments over your repayment term.
Open calculatorStudy Hours Calculator
Plan weekly study hours from credit load and exam dates.
Open calculatorSwimming Calories Calculator
Estimate calories burned swimming from duration, stroke, and weight.
Open calculatorTarget Heart Rate Calculator
Set target heart rate zones for cardio training intensity.
Open calculatorTDEE Calculator
Find daily calorie needs based on activity level and body stats.
Open calculatorTemperature Converter
Convert temperatures between Celsius, Fahrenheit, and Kelvin.
Open calculatorTest Score Calculator
Convert points earned into percentage and letter grade.
Open calculatorThermal Expansion Calculator
Estimate material expansion from temperature change and coefficient.
Open calculatorTile Calculator
Estimate tile count from room area, tile size, and grout spacing.
Open calculatorTime Converter
Convert durations between seconds, minutes, hours, and days.
Open calculatorTime Duration Calculator
Find elapsed hours and minutes between two clock times, including overnight spans.
Open calculatorTime Zone Calculator
Convert date and time between UTC offsets worldwide.
Open calculatorTip Calculator
Split a bill and tip fairly by calculating the tip, grand total, and amount per person.
Open calculatorTire Size Calculator
Compare tire dimensions and overall diameter across size codes.
Open calculatorTowing Capacity Calculator
Estimate safe towing capacity from GVWR, curb weight, and cargo.
Open calculatorTV Size Calculator
Choose TV screen size from viewing distance and room layout.
Open calculatorUnit Converter
Convert common length, weight, and temperature measurements with one simple tool.
Open calculatorUnix Timestamp Converter
Convert Unix timestamps to readable dates and back.
Open calculatorUpload Time Calculator
Estimate file upload time from size and upload bandwidth.
Open calculatorUUID Generator
Generate random UUIDs for apps, databases, and testing.
Open calculatorVariance Calculator
Calculate statistical variance for a list of values.
Open calculatorVelocity Calculator
Find velocity from distance traveled and elapsed time.
Open calculatorVO2 Max Calculator
Estimate VO2 max from resting heart rate, age, and activity level.
Open calculatorVoltage Drop Calculator
Estimate voltage drop across wire length, gauge, and load.
Open calculatorVolume Converter
Convert volume units for liquids, containers, and recipes.
Open calculatorWaist-to-Hip Ratio Calculator
Assess waist-to-hip ratio as a simple body composition indicator.
Open calculatorWalking Calories Calculator
Estimate calories burned walking from distance, time, and weight.
Open calculatorWallpaper Calculator
Estimate wallpaper rolls from wall area, roll size, and pattern repeat.
Open calculatorWater Intake Calculator
Estimate a practical daily water target based on body weight and exercise time.
Open calculatorWater Usage Calculator
Estimate household water use from fixtures, people, and habits.
Open calculatorWatt Calculator
Calculate electrical power from voltage and current.
Open calculatorWeek Number Calculator
Find ISO week number for any calendar date.
Open calculatorWeight Converter
Convert weight between kilograms, pounds, ounces, and grams.
Open calculatorWeighted Grade Calculator
Calculate weighted course grades from category scores.
Open calculatorWilks Calculator
Compare powerlifting strength across weight classes with the Wilks score.
Open calculatorWork Hours Calculator
Calculate paid hours from clock-in, clock-out, and break time.
Open calculatorBuilt for clarity
The formula is never a black box.
We show how every result is calculated, include practical examples, and explain where estimates have limits.