Free calculators

Free calculators

Get your numbers. Then get numbers that update themselves.

Get your numbers. Then get numbers that update themselves.

Evidence-based BMI, TDEE and protein calculators — the same starting formulas Fettle uses before its Engine takes over.

Evidence-based BMI, TDEE and protein calculators — the same starting formulas Fettle uses before its Engine takes over.

These calculators are for general information only and are not medical advice. Estimates use population-level formulas (BMI; Mifflin-St Jeor RMR; g/kg protein ranges) and may not reflect individual circumstances. Consult a healthcare professional before making significant changes to diet or exercise, particularly if you are pregnant, under 18, or managing a medical condition.

FETTLE

Stop recalculating your life. Start checking in.

Two minutes a week. The Engine does the rest — right down to the shopping.

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FETTLE

Stop recalculating your life. Start checking in.

Two minutes a week. The Engine does the rest — right down to the shopping.

Image

FETTLE

Stop recalculating your life. Start checking in.

Two minutes a week. The Engine does the rest — right down to the shopping.

Image

©2026 Fettle Fitness Ltd · Registered in England & Wales · Fettle® is a registered trade mark of Fettle Fitness Ltd (UK00004371666)

©2026 Fettle Fitness Ltd · Registered in England & Wales · Fettle® is a registered trade mark of Fettle Fitness Ltd (UK00004371666)

©2026 Fettle Fitness Ltd · Registered in England & Wales · Fettle® is a registered trade mark of Fettle Fitness Ltd (UK00004371666)