How to calculate weight loss percentage: the fair formula for your challenge 🧮
📐 The formula
Weight loss in percent
(starting weight − current weight) ÷ starting weight × 100
In other words: divide what you’ve lost by your starting weight and multiply the result by 100.
🔢 Two examples
Person A
Start 100 kg, now 95 kg. Lost: 5 kg. 5 ÷ 100 × 100 = 5%.
Person B
Start 70 kg, now 66.5 kg. Lost: 3.5 kg. 3.5 ÷ 70 × 100 = 5%.
In percent they are level. In kilos, A looks like they achieved far more (5 versus 3.5 kg).
⚖️ Why percent is fairer
Whoever starts heavier usually loses kilos faster. If the heaviest person wins automatically, lighter fighters have little reason to join in. Percent scoring compares everyone with themselves – so everyone has the same chance. More on fair rules: weight loss challenge rules.
🧮 Small calculator
Calculator
Result: –
🥊 FatFight calculates it for you
On FatFight you don’t need to work anything out: the leaderboard shows kg or percent and updates with every entry. If you’d rather keep your weight private, only your change is shown – or you set the whole fight to “percent only”.
🤔 Limits of the percent calculation
Percent is also just a snapshot: weight fluctuates daily with water, salt, food and time of day, so one day’s number says little. And more percent is not automatically better – slow, steady change is generally considered more sustainable than crash diets. That is why the FatFight Leaderboard and the Local Gym Fight count at most 3% per week. With existing health conditions or any doubt, ask your doctor.
🚀 Start in one minute
- 1. Open fatfight.de, enter your weight and name.
- 2. Choose “Against my friends”.
- 3. Send the invite link to your group – done. No app store needed.
❓ Frequently asked questions
How do I calculate weight loss percentage?
Calculate (starting weight − current weight) ÷ starting weight × 100. Example: going from 100 kg to 95 kg is 5 percent weight loss.
Why is percent fairer than kilos?
Whoever starts heavier usually loses kilos faster. Percent accounts for the starting weight, so lighter and heavier fighters have the same chance.
Is 5 kg from 100 kg the same as 3.5 kg from 70 kg?
Yes, both are 5% in percent. In kilos, 5 and 3.5 look different, but relative to the starting weight the achievement is the same.
Does FatFight calculate this automatically?
Yes. The leaderboard shows kg or percent and updates with every entry. You can also set the whole fight to “percent only”.
📚 Keep reading
FatFight is not nutritional or medical advice.