Weight loss percentage calculator.
Weight loss percentage is the share of your starting body weight you have lost: (starting weight - current weight) / starting weight x 100. Go from 90 kg to 84 kg and that is a 6 kg loss, or 6 / 90 x 100 = 6.7% of your body weight. Enter your two weights below, in kg or lb, for the percentage, the total lost, and - if you add a goal - how fast you would need to move.
By Markus Evers Updated August 19, 2026 Method: Percent-of-bodyweight change formula
Sources
- National Heart, Lung, and Blood Institute (1998), Clinical Guidelines on Overweight and Obesity in Adults
- Wishnofsky M (1958), American Journal of Clinical Nutrition
Your weight loss percentage
6.7 %
That is 6 kg off a starting weight of 90 kg.
Progress toward goal
0 %
Rate needed for your timeframe
-
Estimates for general fitness tracking, not medical advice. The percentage is exact from the two weights you enter; the weekly-rate guidance uses about 0.5 to 1% of body weight per week as a widely cited range, not a hard rule. Read the trend over several weeks rather than any single weigh-in.
the short answer
Weight loss percentage is how much of your starting body weight you have lost, as a percentage: percentage lost = (starting weight - current weight) / starting weight x 100. A drop from 90 kg to 84 kg is 6 / 90 x 100 = 6.7%. The unit cancels, so 200 lb to 185 lb is the same sum: 15 / 200 x 100 = 7.5%. That is the whole method - the calculator just applies it to your numbers and, if you add a goal and a timeframe, works out the weekly rate it would take.
How to calculate percentage of body weight lost.
Start with the loss itself: total lost = starting weight - current weight. Then turn it into a share of where you began: percentage lost = total lost / starting weight x 100. Dividing by the starting weight, not the current one, is the convention, and it is what keeps the number comparable over time. A client who starts at 90 kg and is now 84 kg has lost 6 kg, which is 6 / 90 x 100 = 6.7%.
If you add a goal weight, the calculator also shows progress toward goal = (starting weight - current weight) / (starting weight - goal weight) x 100. Starting at 90 kg, now 84 kg, aiming for 80 kg, that is 6 / 10 x 100 = 60% of the way there. Add a timeframe and it divides what remains by the weeks - required weekly rate = (current weight - goal weight) / weeks - then expresses that as a percentage of your current body weight so you can read it against a sensible pace.
Everything above is unit-agnostic, because a percentage is a ratio: 200 lb down to 185 lb gives the same 7.5% whether you think in pounds or convert to kilos first. Toggle kg or lb at the top of the calculator and the percentage does not budge - only the "total lost" and "rate per week" labels change unit.
Why percentage beats absolute kilos for comparing progress.
Five kilograms is not the same achievement for everyone. For someone starting at 70 kg it is a 7.1% change; for someone at 120 kg it is 4.2%. Same number on the scale, very different relative effort and very different visual result. Percentage normalises for body size, so it is the fair way to compare two people, or to compare your own progress across a longer, heavier phase and a shorter, lighter one.
It also keeps expectations honest as you get lighter. The same weekly kilo becomes a bigger slice of a smaller body, which is exactly why loss tends to slow near the end - the percentage view makes that predictable instead of demoralising. When you want the fuller picture of what is actually changing, the scale is only one signal; see how to track progress beyond the scale.
The 0.5 to 1% per week guideline.
A commonly used pace is about 0.5 to 1% of body weight per week. For a 90 kg person that is roughly 0.45 to 0.9 kg a week; 0.9 kg sits at the upper, harder-to-hold end. Treat this as guidance, not a medical rule - it is a range coaches lean on because it usually protects muscle, energy, and adherence, and because it maps neatly onto the percentage view this tool is built around.
The honest headline is that sustainable beats fast. A gentler rate you can hold for months almost always finishes ahead of a sharp cut you abandon in week three, and pushing past roughly 1% a week tends to trade lean mass and daily energy for a number that rebounds. If the rate your timeframe demands lands above that range, the calculator flags it - the fix is usually more weeks, not more deficit.
Why the scale lies from one week to the next.
A single weigh-in is noisy. Most short-term swings are water, not fat: glycogen stored in your muscles holds water alongside it, so a higher-carb day, extra sodium, a hard training session, or a normal hormonal shift can move the scale a kilo or two overnight with no change in body fat at all. Take one snapshot on a bad water day and your loss percentage can look like it reversed when nothing real happened.
The fix is to zoom out. Weigh in consistently, read a weekly average and the percentage trend across several weeks, and judge direction rather than any one morning. If the trend genuinely stalls for a few weeks, that is a different problem - here is how to break through a plateau. To set the target itself, the goal weight date calculator turns a goal and a pace into a date.
How coaches track weight loss percentage for clients.
For a coach, the percentage is the number that travels. It lets you line up a 70 kg client and a 120 kg client on the same chart, praise real progress fairly, and spot a stall early - a client stuck at the same percentage for a few weeks gets a check-in, not a wait-and-see. Talking in percentage of body weight per week also keeps the pace conversation calm: "you are moving at about 0.7% a week, which is right where we want it" lands better than a raw kilo count that means nothing without the starting weight.
The hard part is doing it for a whole client list at once. Inside Coachway, each client's weigh-ins, weekly average, and percentage trend sit next to their training, check-ins, and messages - one tab per client instead of a spreadsheet, a chat app, and a photo folder - so re-checks and honest progress conversations are already prepared when the week comes around.
Track weight, weekly averages, and percentage trends for your whole client list from one tab.
No charge today - cancel anytime under Billing.Turn the percentage into a check-in message
Paste the loss, the percentage and the weeks and the model drafts the check-in message that names the percentage, reads it against the 0.5 to 1 percent guideline on this page and sets the next milestone in your voice. The rest of the check-in prompts are in ChatGPT prompts for client check-in replies.
Turn the percentage into a check-in message
When to use it: Each week the client weighs in, or at a milestone.
What to paste in: The kg lost, the percentage, the weeks, a client ID, one of your own messages.
This weight loss percentage calculator says a client has lost [KG] kg, [PERCENT] percent of their starting weight, in [WEEKS] weeks (client ID [ID]). Write the weekly check-in message in my voice that names the percentage once, says what it means against the 0.5 to 1 percent a week guideline from the page, names the next milestone in kg, and asks one question they can answer with a number. Under 90 words. Write like me: [PASTE ONE OF YOUR OWN MESSAGES]. Do not change the calculator's numbers; do not add medical advice; if anything needed is missing, ask me before assuming. Client ID [ID], no name.
Frequently asked questions.
How do I calculate percentage of body weight lost?
Take your starting weight, subtract your current weight, divide by the starting weight, and multiply by 100: percentage lost = (starting weight - current weight) / starting weight x 100. Going from 90 kg to 84 kg is a 6 kg loss, and 6 / 90 x 100 = 6.7% of your body weight. The unit does not matter - 200 lb down to 185 lb is 15 / 200 x 100 = 7.5% - because a ratio cancels the unit out.
What percentage of weight loss is noticeable?
It is individual and depends heavily on your starting size, where you carry weight, and how you measure "noticeable". Many people first notice change in how clothes fit and in progress photos rather than in the mirror, often somewhere in the low single-digit percentages, but there is no fixed threshold that holds for everyone. Percentage is more useful here than kilograms because the same 3 kg reads very differently on a lighter and a heavier body.
Why use percentage instead of kilograms to track progress?
Percentage normalises for body size, so it lets you compare progress fairly across two different people or two phases of your own journey. Losing 5 kg is a bigger relative change for someone at 70 kg (7.1%) than at 120 kg (4.2%), even though the scale moved the same amount. That is why coaches often talk in percentages and weekly rates as a percentage of body weight rather than in raw kilos.
Is losing 1% of body weight per week a safe rate?
About 0.5 to 1% of body weight per week is a widely used guideline for a manageable pace, not a hard medical rule. The upper end is harder to hold and, done through a large deficit, tends to cost more muscle and adherence than a gentler pace. Slower and sustainable usually beats fast: a rate you can keep for months out-performs a sharp drop you abandon. If you have a medical condition or a history of disordered eating, work with a healthcare professional.
Why does the scale change so much from day to day?
Daily scale weight swings mostly reflect water, not fat. Glycogen stored in muscle holds water with it, so more carbs, more sodium, harder training, and normal hormonal shifts can move the number a kilo or two overnight with zero change in body fat. That is why a single weigh-in is noisy - read a weekly average and the percentage trend over several weeks, and pair the scale with measurements, photos, and performance rather than trusting one morning number.
Can ChatGPT write the weight loss update for my client?
Yes: paste the kilos, the percentage and the weeks from this calculator with one of your own messages and it writes the check-in that names the percentage once, reads it against the 0.5 to 1 percent a week guideline and sets the next milestone. It must not add calorie or medical advice; the prompt on this page says so.
This calculator is general fitness and progress math, not medical, dietary, or clinical advice. The percentage is exact; the pace guidance is a broad range, not a prescription. If you have a medical condition or a history of disordered eating, work with a healthcare professional.
Keep building the plan: set a date with the goal weight date calculator, find the intake behind your pace with the calorie deficit calculator and TDEE calculator, or split those calories with the macro calculator.
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