About Fitness Calculator
Updated 10 October 2026
11 free calculators, metric or imperial, no account. Each one shows you the calculation it ran, works through an example and says where the result stops being useful.
The tools
- BMI Calculator for Adults. Weight against height, scored on the adult bands, with the healthy weight range for your height.
- Calorie Calculator. How much to eat to lose, hold or gain weight, with the deficit and surplus worked out for you.
- TDEE Calculator. What you burn across a whole day, from resting energy expenditure and the activity band you pick.
- BMR Calculator. Your resting burn through all three standard formulas at once, so you can see how far apart they land.
- Macro Calculator. Daily grams of protein, carbohydrate and fat for your calories, with the split you choose.
- Protein Calculator. Grams of protein a day from your weight and your training, printed as a range because the research is one.
- Navy Body Fat Calculator. Body fat percentage from neck, waist and hip, using the United States Navy tape method.
- Ideal Weight Calculator. Four classic formulas side by side, checked against the healthy BMI band for your height.
- Water Intake Calculator by Weight. A daily fluid target from body weight, with an allowance added for the training you do.
- Army Body Fat Calculator. The waist-to-height standard the Army adopted in July 2026, with the largest waist that still passes at your height.
- ACFT Calculator. Points for all five AFT events against the official scales, on either the general or the combat standard.
Methods and checks
Calories use the Mifflin–St Jeor equation with an activity factor you pick separately. The body-fat and ideal-weight tools use the equations named on their own pages. The water rule is a planning heuristic, not a validated personal fluid prescription, which is why that page spends as long on its limits as on its sums.
The September 2026 tool updates were checked against reference calculations, unit conversions and invalid inputs. The male Mifflin equation at age 30, 70 kg and 175 cm gives 1,648.75 kcal/day, and BMI comes out at about 22.86. Those checks tell you the sums are right. Whether a formula fits you is a separate question, and every page says so.
Editorial responsibility
The site publishes under the pen name Rowan Hale, who claims no medical or dietetic qualification. Research, editing and software development here are AI-assisted, with editorial responsibility resting on the site operator. The guides have had no independent clinical review.
Sources let you check a claim for yourself. A citation still cannot tell you whether the advice around it suits your situation, and the editorial policy sets out the sourcing, the corrections and the limits.
Privacy and funding
The calculator code runs in your browser, and your measurements stay there. Optional analytics and the contact form handle information separately, as the privacy policy explains.
The tools are free. Google AdSense pays for them, which means ads run on these pages and Google and its partners may store or read identifiers on your device. Readers in the UK, the EEA and Switzerland get non-personalised ads, because serving the personalised kind there needs a certified consent platform and this site does not run one. Analytics stays off until you accept it.
So if you hit a reproducible error, send the tool URL and made-up example inputs through Contact. For a question about your own health, ask a qualified professional. The disclaimer explains what these tools are for.