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How long it actually takes
Every calculator hands you a deficit. Almost none show you the calendar, which is the part that decides whether you are still doing this in March.
Short answer
A 500-calorie daily deficit takes off roughly half a kilo, or one pound, a week. Losing 10 kg at that pace takes about twenty weeks, not the six that most before-and-after photos imply. Bigger deficits do work faster, up to the point where they stop being liveable.
Step 1 · Your details
That is your maintenance minus a deficit you can actually hold. Falling under it occasionally is normal; living under it is how people end up quitting in week three.
Your weight, week by week
This is the graph that never appears on other calculators, and it is the only one that tells you whether the plan fits your life.
The flag is your goal weight. The line is arithmetic, not a promise: real weight loss stalls, jumps with water retention, and slows as you get lighter, because a smaller body burns less. Expect the shape, not the exact dates.
About 20 weeks. Not exciting, but it is the version that is still happening at Christmas.
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What this page cannot do
Every plan works on paper. Mango Bites is built for week three.
The arithmetic above is the easy half. The hard half starts when the novelty wears off, the scale stalls for nine days, and nobody is watching. The app is designed for exactly that stretch: streaks, quests, and a mascot whose day depends on yours.
- Your calorie target recalculates itself as you get lighter, so the plateau this page warns about does not catch you out
- Photograph meals instead of typing them, which is the difference between tracking for three weeks and tracking for a year
- Streaks, daily quests and levels that make consistency feel like progress rather than restriction
- Mangi reacts to your day, which turns out to be far harder to abandon than a spreadsheet
What to do with this
Weigh weekly, not daily
Day-to-day weight is mostly water, salt and what is still in transit. A weekly average is the only number with enough signal in it to act on.
Hold protein while calories fall
In a deficit, protein decides whether the loss comes from fat or from muscle. Keep it high and take the cut out of carbs or fat instead.
Recalculate every 5 kg
A lighter body burns less. The deficit that worked at the start becomes maintenance eventually, which is what a plateau actually is.
How this is worked out
Mifflin-St Jeor, with two guardrails
maintenance = Mifflin-St Jeor BMR × activity · 1 kg of fat ≈ 7,700 kcal · deficit = weekly loss × 7,700 ÷ 7
Maintenance comes from Mifflin-St Jeor, which predicts resting metabolic rate more accurately than the older Harris-Benedict equation for most people, multiplied by an activity factor between 1.2 and 1.9.
The conversion assumes roughly 7,700 kcal per kilogram of body fat. 3,500 per pound. It is a serviceable approximation rather than a law of physics, and it gets less accurate the longer a diet runs, because the body adapts.
Then two guardrails, and the tighter one wins. Never below 1,200 kcal for women or 1,500 for men, because under that it becomes very hard to get adequate micronutrients from food. And never more than 25% below maintenance, because larger cuts reliably cost muscle, tank training performance, and produce the rebound that makes aggressive diets slower than patient ones over a year.
These exact guardrails ship in the app. calculateWeightLossTimeline runs Mifflin-St Jeor, applies your chosen pace, and clamps intake at 1,200 kcal for women and 1,500 for men, recalculating the real deficit when the floor is hit rather than quietly promising a timeline it cannot deliver. Mango Bites would rather tell you the honest week count than the flattering one, which is the whole reason the app recalculates as you get lighter.
What each pace actually costs
Daily deficit required, and the time to lose 10 kg.
| Pace | Per week | Daily deficit | 10 kg takes |
|---|---|---|---|
| Gentle | 0.25 kg / 0.55 lb | 275 kcal | 40 weeks |
| Steady | 0.5 kg / 1.1 lb | 550 kcal | 20 weeks |
| Brisk | 0.75 kg / 1.65 lb | 825 kcal | 13 weeks |
| Fast | 1.0 kg / 2.2 lb | 1,100 kcal | 10 weeks |
Questions people ask
How big should a calorie deficit be?
How big should a calorie deficit be?
Between 15% and 25% of your maintenance calories for most people, which usually lands somewhere between 300 and 700 a day. The right size is the largest one you can hold without your sleep, training and mood falling apart, and that ceiling is personal.
How much weight can I safely lose per week?
How much weight can I safely lose per week?
Around 0.5 to 1% of body weight a week is the range most clinicians and sports dietitians work within. For an 80 kg person that is 0.4 to 0.8 kg. Faster than that and an increasing share of what you lose is muscle rather than fat.
Why have I stopped losing weight?
Why have I stopped losing weight?
Usually one of three things. A lighter body burns fewer calories, so the deficit that worked at 90 kg is smaller at 82 kg. Portions drift upward over weeks without anyone noticing. Or you are losing fat and holding water at the same time, which hides real progress on the scale for a week or two at a stretch.
Is 1,200 calories a day safe?
Is 1,200 calories a day safe?
It is the conventional floor for women rather than a target, and it is hard to hit adequate protein, iron, calcium and B vitamins underneath it from food alone. If a calculator is telling you to eat 1,200, the better move is usually a slower pace, not a smaller plate.
Does the 3,500 calories per pound rule actually work?
Does the 3,500 calories per pound rule actually work?
As a starting approximation, yes. Over longer diets it overestimates loss, because it assumes your metabolism stays fixed while you shrink, and it does not. Treat the timeline here as an optimistic straight line that reality will bend.
Is BMI a useful measure?
Is BMI a useful measure?
It is a decent population statistic and a poor individual one. It cannot tell muscle from fat, which is why lean, muscular people routinely read as overweight. It is shown here for context only. The number worth watching is the direction your weight is moving, not which bracket it falls in.
Sources
This is an estimate, not medical advice. Formulas like these describe averages, and you are a person rather than an average. Medication, thyroid conditions, pregnancy, breastfeeding and a history of disordered eating all move these numbers. Talk to a doctor or a registered dietitian before making a big change.
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