ReckonBox logoReckonBox
Free, no signup

Calculators that show the math.

Precise readings, the formula behind every result, and no account to create. Built to work on any device.

Browse by category

Finance

Finance calculators and tools.

India Finance

India Finance calculators and tools.

Auto

Auto calculators and tools.

Health & Fitness

Health & Fitness calculators and tools.

Date & Time

Date & Time calculators and tools.

Utilities

Utilities calculators and tools.

Home & Construction

Home & Construction calculators and tools.

AI

AI calculators and tools.

Business

Business calculators and tools.

Popular tools

BMI Calculator

Find your body mass index, weight category, and healthy weight range for your height, using either the WHO or the Asian BMI cutoffs.

BMR Calculator

Find your basal metabolic rate from three formulas at once: Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.

TDEE Calculator

Find your total daily energy expenditure from your activity level, and the daily calories to lose, maintain, or gain weight.

Body Fat Calculator

Estimate your body fat percentage with the US Navy tape method from three measurements, plus your fat mass, lean mass, and FFMI.

Macro Calculator

Turn your calories into daily protein, carbs, and fat, with presets for balanced, low-carb, high-protein, and keto.

Calorie Calculator

Work out how many calories to eat a day to lose, maintain, or gain weight, with your choice of the Mifflin or Harris-Benedict formula.