Smart Financial Calc

Fitness Calculators

Population-level estimates for adults — BMI, energy needs, pace and strength — with the equations named and their limits stated. Not medical advice.

Calculators

  • Adult BMI Calculator

    Body mass index for adults in metric or US units, with what BMI does not measure.

  • BMR Calculator

    Estimated basal metabolic rate using the Mifflin–St Jeor equation.

  • TDEE Calculator

    Estimated daily energy expenditure from BMR and an activity factor you choose.

  • Pace Calculator

    Solve for pace, distance or time in miles or kilometers, with split times.

  • Race Time Predictor

    Estimate a finish time from a recent race using Riegel’s formula, with its limits.

  • One-Rep Max Calculator

    Estimate a one-repetition maximum with Epley, Brzycki and other named formulas.

Choosing a fitness estimate

These calculators give population-level estimates for adults from published equations. They are useful for planning and say less about any one person, so treat each result as a starting point.

Is my weight in the usual range for my height?

Adult BMI Calculator

Adult BMI with the standard category cut-offs and the healthy-weight range for your height.

How many calories do I use?

BMR Calculator TDEE Calculator

Resting energy from the Mifflin–St Jeor equation, with other equations for comparison, then daily expenditure using an activity multiplier you can see and change.

What pace do I need for a finish time?

Pace Calculator

Pace, time or distance from the other two, with presets for common race distances and a split for every mile or kilometer.

What could I run at another distance?

Race Time Predictor

Riegel’s formula applied to a recent result, with a warning when the prediction reaches far beyond it.

What is my one-rep max?

One-Rep Max Calculator

Several published formulas side by side, from a weight lifted for a number of reps, with loads for common percentages.

Have these to hand

  • A recent weight and height, measured rather than remembered.
  • A recent race or timed run over a known distance.
  • A set taken close to failure, ideally ten reps or fewer.

Mistakes that change the answer

  • Reading BMI as a body-fat measurement. It cannot tell muscle from fat.
  • Treating a calorie estimate as exact; a person can differ from the equation’s prediction by a meaningful amount.
  • Predicting a marathon from a 5K without the endurance training the longer race demands.
  • Applying adult equations to children, or during pregnancy, where they do not hold.
  • How accurate are BMI, BMR and TDEE estimates?

    The equations behind these numbers describe groups of adults, not you. One worked example shows how far each estimate can move, which choices matter most, and how to check the result against real life.

  • Unit conversion pitfalls: gallons, tons, cups, GB vs. GiB

    Nine unit traps with the numbers worked out: US vs. imperial gallons and pints, fluid ounces vs. ounces, three kinds of ton, cups of flour in grams, cup and tablespoon sizes, GB vs. GiB, bits vs. bytes, temperature changes and UK vs. US mpg.