Weight Loss Percentage Calculator
See what share of your starting weight you have lost. Works in pounds, kilograms or stones — the units cancel out.
Start weight and now
Amount lost
20
Current as a share of start
90%
Weight lost
10%
(200 − 180) ÷ 200 × 100
The formula
Weight loss % = (Start weight − Current weight) ÷ Start weight × 100
The units cancel in the division, so pounds, kilograms and stones all give the same percentage. Only make sure both boxes use the same one.
Worked example — 200 lb down to 180 lb
200 − 180 = 20
20 ÷ 200 = 0.1
0.1 × 100 = 10
So that is a 10% loss.
Why a percentage rather than a number
A percentage makes progress comparable across body sizes. Twenty pounds is 6.7% of a 300 lb starting weight and 14.3% of a 140 lb one. The same number describes two very different journeys; the percentage does not.
This is also why clinical research reports weight change in percent. It is the only way to pool results across people who started at different weights.
The measurement itself moves
Body weight swings by a few pounds within a single day from water, food in transit and glycogen. A weekly average taken at the same time of day, in the same clothing, tracks a trend far better than any one reading.
Weight also does not distinguish fat from muscle or water. Someone training hard can lose fat while the scale barely moves.
The 5% and 10% milestones
Clinical studies commonly use 5% of starting weight as the point where measurable benefits appear, and 10% as a further milestone. These are research conventions, not personal targets.
The threshold comes from the 2013 AHA/ACC/TOS guideline, which the National Heart, Lung, and Blood Institute publishes. It reports that a sustained loss of 3% to 5% of body weight is enough to produce clinically meaningful changes in triglycerides, blood glucose and the risk of type 2 diabetes, and that larger losses improve blood pressure and cholesterol further.
Any weight goal, and how fast to approach it, is worth setting with a clinician who knows your history — particularly alongside a medical condition or a medication that affects weight.
Common questions
- How do I calculate weight loss percentage?
- Weight loss percentage = (starting weight − current weight) ÷ starting weight × 100. The units cancel, so pounds and kilograms give the same answer.
- Does it matter whether I use pounds or kilograms?
- No, as long as both weights use the same unit. The division cancels the units out, so the percentage is identical either way.
- Why is weight loss reported as a percentage?
- Because it makes progress comparable between people of different sizes. Losing 20 lb means something different at 300 lb than at 140 lb; losing 5% means the same thing at both.
- What percentage of body weight loss is considered meaningful?
- Clinical studies commonly treat 5% as the point where measurable health benefits appear, and use 10% as a further milestone. Discuss any target with a clinician who knows your history.