Weight Loss Percentage Calculator (% of starting weight lost)

Understanding the weight loss percentage calculator — concept and principle

This calculator shows how much weight you have lost as a percentage of your starting weight, how fast you are losing on average, and how far along you are toward your goal. Percentages are useful because health benefits are usually described as a share of starting weight.

Loss ÷ starting weight: with the default inputs the result is 6% (55% of the way to 82 kg).

How it is calculated

Weight lost (%) = (starting weight − current weight) ÷ starting weight × 100

Average loss per week = weight lost ÷ weeks

Weight at 5% and 10% loss = starting weight × 0.95 and × 0.90

Progress toward goal (%) = weight lost ÷ (starting weight − goal) × 100

A negative percentage means weight was gained.

The principle

Comparing loss as a percentage makes results fair between people of different sizes: 5 kg is a bigger change for a 60 kg person than for a 120 kg person. Obesity guidelines note that a sustained loss of about 3–5% starts to improve blood sugar, blood fats and blood pressure, with larger benefits at 5–10% and beyond.

Worked example

Default inputs: start 92 kg, now 86.5 kg, goal 82 kg, 12 weeks.

Weight lost = 92 − 86.5 = 5.5 kg = 5.5 ÷ 92 = 5.98% → 6%.
Average per week = 5.5 ÷ 12 = 0.46 kg.
5% mark = 87.4 kg; 10% mark = 82.8 kg.
Progress = 5.5 ÷ (92 − 82) = 55%; still to lose 4.5 kg.

Each point is the calculator re-run with only “Starting weight (kg)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Starting weight (kg)	Weight lost
23	-276.1%
46	-88%
69	-25.4%
92	6%
115	24.8%
138	37.3%
184	53%

How to read the result

Where does your result fall?

Passing the 5% mark is a meaningful milestone for health. A pace of about 0.5–1 kg a week is generally considered sustainable. Weight naturally fluctuates by 1–2 kg from day to day, so look at the weekly trend rather than single readings.

Common mistakes

Comparing weights taken at different times of day or with different clothes.
Expecting steady weekly loss; plateaus are normal.
Losing weight much faster than 1 kg a week for long periods without medical supervision.

Keep in mind: This is general information, not medical advice. Unintended weight loss should be checked by a doctor.

Frequently asked questions

What is a healthy rate of weight loss?

About 0.5–1 kg a week for most adults.

Why does 5% matter?

Losses of about 3–5% already improve several cardiovascular risk factors.

Why has my weight loss slowed?

A smaller body uses less energy, and water shifts can mask fat loss for a while.

Sources: Jensen MD, Ryan DH, Apovian CM, et al., "2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults", Circulation 2014;129(25 Suppl 2):S102–S138

Checked 9 Nov 2026. Jensen MD et al., 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults, Circulation 2014;129(25 Suppl 2):S102–S138 (3–5% sustained loss clinically meaningful; 5–10% within 6 months as an initial goal).

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