Free tools, with nothing to sign up for
25 calculators and timers for the numbers around building a habit: what your body is doing, when to sleep, how long to work, and whether you are actually on track. Every one of them runs entirely in your browser.
Body
Estimates from published formulas, with an honest account of what each one cannot see.
BodyBMI calculator
Enter height and weight. The number appears as you type, and nothing leaves your browser.
BodyCalorie calculator
Estimates how many calories you burn in a day, and what to eat to hold, lose, or gain weight.
BodyWater intake calculator
A weight-based estimate of daily fluid, adjusted for exercise and heat.
BodyBody fat calculator
The US Navy circumference method. All you need is a tape measure.
BodyIdeal weight calculator
Four published formulas, side by side, plus the healthy BMI range for your height.
BodyMacro calculator
Turns a calorie target into grams of protein, carbs, and fat.
BodyProtein calculator
How much protein a day, and roughly what that looks like on a plate.
BodyWaist to height ratio
One measurement, one division, and a better risk screen than BMI.
Fitness
Training numbers worth knowing, and the ones that mislead if you read them wrong.
FitnessHeart rate zones
Five training zones from your age, with an option for the more accurate reserve method.
FitnessRunning pace calculator
Give it any two of pace, time, and distance, and it works out the third.
FitnessOne rep max calculator
Estimate a one rep max from a set you actually did, with the working percentages.
FitnessCalories burned
Pick an activity and a duration. MET values do the rest.
Sleep and time
Timers and schedules that keep accurate time even when the tab is in the background.
Sleep and timeSleep calculator
Work backwards from your alarm, or forwards from bedtime, in whole sleep cycles.
Sleep and timePomodoro timer
Twenty-five minutes of work, five off, a longer break every fourth round. Adjustable if that split does not suit you.
Sleep and timeInterval timer
Set work and rest, choose your rounds, and go. Includes a Tabata preset.
Sleep and timeCountdown to a date
Days, hours, and minutes to any date, ticking live.
Sleep and timeSleep debt calculator
Enter the last seven nights. See what you are actually carrying.
Sleep and timeStopwatch
Start, lap, stop. Keeps time correctly even in a background tab.
Everyday maths
The arithmetic behind keeping something up, and the everyday sums around it.
Everyday mathsHabit streak calculator
How long your streak is, what rate you are running at, and how much room you have left.
Everyday mathsPercentage calculator
The four percentage questions people actually search for, each with the working shown.
Everyday mathsAge calculator
Exact age from a date of birth, plus total days lived and the countdown to your next birthday.
Everyday mathsDate difference calculator
Total days, working days, and the same span expressed in weeks and months.
Everyday mathsUnit converter
Length, weight, temperature, and volume, converted as you type.
Everyday mathsReading time calculator
Paste text or enter a word count, and get reading and speaking times.
Everyday mathsTime duration
Hours and minutes between two times, including shifts that cross midnight.
Why none of these ask for your email
A calculator that wants an account before it will show you a number is not a calculator, it is a form. Every tool here does its arithmetic in your browser and shows the answer as you type. There is no submit button because there is nothing to submit.
That also means we never see what you enter. Your weight, your date of birth, and your sleep schedule are typed into your own device and stay there. Close the tab and they are gone, including from us, because they were never here.
The tradeoff is real and worth naming: nothing is remembered between visits. You retype your details each time. Saving them would mean storing them, and for a page that exists to answer one question in ten seconds, that is the wrong trade.
The tracker is the part that remembers
If you want to watch a number move over months rather than read it once, that needs an account and a record. Free while in early access.
Start tracking