Weight Loss Percentage Calculator

See what share of your starting weight you have lost. Percentages make progress comparable across different starting weights, which is why weight-loss challenges are scored this way rather than in raw pounds.

Enter your numbers and press Calculate — the full working appears here.

The weight loss percentage formula

The loss is measured against where you started, which is what makes the figure fair between two people at very different weights.

((Starting weight − Current weight) ÷ Starting weight) × 100

((200 − 180) ÷ 200) × 100 = 10%

Units cancel out, so pounds, kilograms and stone all give the same percentage.

Worked example

You started at 92 kg and now weigh 84.5 kg. What percentage have you lost?

Find the weight lost.92 − 84.5 = 7.5 kg
Divide by the weight you started at.7.5 ÷ 92 ≈ 0.0815
Multiply by 100.0.0815 × 100 ≈ 8.15%

Answer≈ 8.15% of starting weight lost

Open this example in the calculator →

Why percentages beat pounds

Two people each lose 15 lb. One started at 180 lb and the other at 320 lb. In raw numbers their results are identical; as percentages they are not close:

15 lb from 180 lb is 8.3% of starting weight.
15 lb from 320 lb is 4.7% of starting weight.

That gap is why workplace and team challenges are almost always scored on percentage rather than pounds — it removes the advantage of simply being heavier at the start.

Clinical significance of percentage milestones

Major medical bodies, including the CDC and NIH, evaluate lifestyle interventions around percentage milestones rather than absolute scale readings:

5% Weight Loss: Clinically proven to lower blood pressure, reduce circulating triglycerides, and improve glycemic markers in pre-diabetic patients.
10% Weight Loss: Associated with marked improvements in cardiovascular risk factors, sleep apnea severity, and osteoarthritis joint loading.

To track changes in body composition rather than total mass, you can estimate changes in lean mass and fat using the body fat percentage calculator.

Working towards a target

To find the weight that represents a given percentage loss, use the percentage calculator: losing 15% from 200 lb means weighing 85% of 200, which is 170 lb.

This is arithmetic, not medical advice

The calculator converts two numbers into a percentage. It knows nothing about your health, body composition or what a sensible target would be for you. For that, speak to a doctor or a registered dietitian. See the full disclaimer.

Frequently asked questions

How do I calculate weight loss percentage?

Subtract your current weight from your starting weight, divide by the starting weight, then multiply by 100. Going from 200 lb to 180 lb is (200 − 180) ÷ 200 × 100 = 10%.

Does it matter whether I use pounds or kilograms?

No. The units cancel out in the division, so the percentage is identical either way — as long as both figures use the same unit. Do not mix pounds and kilograms in one calculation.

What is a healthy rate of weight loss?

There is no single weekly rate that is right for everyone. A healthcare professional can advise based on your health and circumstances. This calculator only does the arithmetic; it cannot assess whether a rate or target is appropriate for you.

Why do weight loss challenges use percentages instead of pounds?

Because a percentage is fair across different starting weights. Losing 10 lb is a much larger achievement for someone starting at 150 lb than for someone starting at 300 lb, and the percentage reflects that while the raw number does not.

How do I calculate the weight I need to reach a target percentage?

Multiply your starting weight by (100 − target) ÷ 100. To lose 15% from 200 lb: 200 × 0.85 = 170 lb. The percentage calculator does this in one step.