Health & Fitness Calculators

17 free calculators · Updated for 2026/27

Health targets are easier to act on when they carry a number, whether that is a daily calorie figure, a training zone or a due date. Health and fitness calculators work from body measurements, activity level and goals to produce those figures, supporting everyday choices about eating, training, drinking and following a pregnancy, for adults and for children.

The BMI Calculator places height and weight in a category and gives a healthy weight range, while the Calorie Calculator (TDEE) turns activity level into a daily intake for losing, maintaining or gaining weight. Five training zones come from the Heart Rate Zone Calculator using the Karvonen formula, the Alcohol Units Calculator counts units in a drink against the NHS weekly guideline, and the Pregnancy Due Date Calculator estimates a due date with trimester milestones from a last period.

B

BMI Calculator

Calculate your Body Mass Index using metric or imperial measurements. See your BMI category and healthy weight range.
C

Calorie Calculator (TDEE)

Calculate your Total Daily Energy Expenditure and recommended calorie intake for weight loss, maintenance or gain.
B

Body Fat Percentage Calculator

Estimate your body fat percentage using the US Navy method with waist, neck and hip measurements.
P

Pregnancy Due Date Calculator

Calculate your estimated due date from your last menstrual period. See key milestones and trimester progress.
A

Alcohol Units Calculator

Calculate alcohol units in your drinks. Track against the NHS guideline of 14 units per week.
S

Sleep Calculator — Bedtime & Wake Time

Find the best bedtime or wake-up time based on 90-minute sleep cycles. Wake feeling refreshed.
P

Pace Calculator (Running)

Calculate running pace, finish time or distance. Supports km and mile splits for 5K, 10K, half marathon and marathon.
W

Water Intake Calculator

Calculate your recommended daily water intake based on weight, activity level and climate.
I

Ideal Weight Calculator

Calculate your ideal weight using Robinson, Miller, Devine and Hamwi formulas. See your healthy BMI range.
S

Steps to Miles/Km Calculator

Convert steps to distance, calories and walking time based on your height and stride length.
H

Heart Rate Zone Calculator

Calculate your 5 heart rate training zones using the Karvonen formula with resting heart rate.
W

Weight Loss Calculator

Calculate how long to reach your target weight with milestones and daily calorie deficit.
P

Protein Intake Calculator

Calculate daily protein needs by weight and goal. See common protein sources per serving.
O

Ovulation Calculator

Estimate ovulation date and fertile window based on your last period and cycle length. See 3 cycles ahead.
M

Macro Calculator — Protein, Carbs & Fat

Calculate daily protein, carbs and fat targets based on your body stats, activity and goal.
W

Waist-to-Hip Ratio Calculator

Calculate your waist-to-hip ratio and cardiovascular disease risk using WHO guidelines.
B

BMI Calculator for Children

Work out your child's BMI centile from age in months, sex, height and weight, using the UK growth reference behind NHS charts, for ages 2 to 18.