Weight loss rate calculator

"Lost 2 kg this month" means something different for a 60 kg client than for a 120 kg client. Turn the change into a percent of body weight per week, and see how long a goal weight really takes.

Why percent of body weight

A fixed number like "1 kg a week" is a big push for a light client and a slow one for a heavy client. A percent scales with the person, so it is easier to compare clients and to keep the pace reasonable as the client gets lighter.

The range this calculator shows

A commonly cited range for lean, training people who want to keep muscle while losing fat is about 0.5–1% of body weight per week (Helms, Aragon and Fitschen, Journal of the International Society of Sports Nutrition, 2014). It is a guideline, not a rule. Clients with more weight to lose often lose faster at the start, and many people do well slower than 0.5%. The calculator only flags a rate outside the range so you look at it; it doesn't say the rate is wrong.

How it's calculated

• Rate per week = (start − now) ÷ weeks.
• Percent per week = rate per week ÷ the average of the start and current weight × 100.
• Weeks to goal assumes the client keeps losing the same percent of their current weight each week, so the weekly amount gets a little smaller as they get lighter: weeks = ln(goal ÷ now) ÷ ln(1 − rate). Real progress is never this smooth; treat the date as a rough guide.

A coaching aid, not medical advice. Clients under 18, pregnant or breastfeeding, or with a medical condition need their own doctor's advice on weight loss. Dizziness, fainting, missed periods, guilt around food or skipping meals to make up for eating are reasons to slow down and involve a professional, not to push the rate.