Weight Loss Timeline Calculator

Week by week

The curve flattens because the deficit column shrinks: a lighter body burns less, so the same plate becomes a smaller deficit every week. A straight-line prediction is the same curve with this column held frozen.

The table above groups the 25 weeks into 7. The amortisation schedule prints every one of them, with the split between interest and principal.

Worked example

A 38-year-old man of 90 kg eating 2,000 kcal a day reaches 80 kg in 25 weeks. The flat 3,500-calorie rule promises it in 21.5, because it never notices that the 513 kcal deficit he starts with has shrunk to 375 by the time he gets there.

How to work it out yourself

1. 1.Enter your current and goal weight, then what you actually eat in a day rather than what you intend to.
2. 2.The date accounts for the deficit shrinking as you get lighter, which is why it is later than a simple division gives.
3. 3.Check the plateau line. That is the weight your current intake maintains on its own; a goal below it will not arrive at this intake, however long you wait.
4. 4.Read the deficit column in the schedule. When it gets small, that is the point to recalculate rather than the point to conclude the diet stopped working.

Time to the goal by daily intake

Eating less does not shorten the timeline in proportion, because the plateau moves down with it. Above about 2,375 calories this person's plateau sits above 80 kg and the goal never arrives at all, which is why the table stops below that.

The formula

1. Maintenance calories at the current weight(10 * 90 + 927.5) * 1.375
2. Deficit right now2512.8125 - 2000
3. Weight this intake eventually maintains(2000 - 1.375 * 927.5) / (10 * 1.375)
4. Goal is reachable at this intake
5. Days to the goallog((90 - 52.704545) / (80 - 52.704545)) / 0.0017857
6. Goal reached on2026-10-02 + 174.80471
7. Weeks to the goal174.80471 / 7
8. Days the flat 3,500 rule predicts(90 - 80) * 7700 / 512.8125
9. Days the flat rule is out by174.80471 - 150.15235
10. Loss rate now512.8125 * 7 / 7700
11. Loss rate on arrival((10 * 80 + 927.5) * 1.375 - 2000) * 7 / 7700
12. Weight to lose90 - 80

Source: Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong? Int J Obes 2013;37:1614, Hall KD. What is the required energy deficit per unit weight loss? Int J Obes 2008;32:573-6, Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241-7, NIDDK Body Weight Planner — the dynamic model this page approximates

Questions people actually ask

Why is this slower than other weight loss calculators?

Because they divide the pounds to lose by a deficit that never changes. Expenditure falls with body mass, so the deficit you start with is not the deficit you finish with. On the worked example the flat rule says 21.5 weeks and the arithmetic that tracks the falling deficit says 25. The difference is not pessimism; it is the term the flat rule drops.

What is the plateau weight?

The weight at which your maintenance calories equal what you are eating, so the deficit reaches zero and loss stops. It is a property of the intake, not of willpower. If your goal sits below it, the intake has to come down or the activity has to go up, and waiting longer will not do it. At very low intakes the figure drops below any weight a person survives at: Mifflin-St Jeor is a straight line and a body is not, so read a plateau far under your goal as 'you keep losing past it', not as a destination.

Does this model metabolic adaptation?

No, and it says so rather than implying otherwise. It models the dominant effect, that a smaller body burns less, and solves that exactly. It does not model the further drop in expenditure beyond what mass alone predicts, which is real, individually variable, and the reason the NIDDK Body Weight Planner exists. Expect real results a little slower than this page, not faster.

Why 7,700 calories per kilogram?

It is the metric form of the 3,500-per-pound convention, and it is the energy density of the mix of fat and lean tissue an average person loses. Hall showed the true figure depends on how much fat you carry to begin with: leaner people need a smaller deficit per unit lost, heavier people a larger one. Treat the date as a good estimate with a couple of weeks either side, not a delivery slot.

Related

• Calorie Needs CalculatorDaily calorie target for a weight goal, and the number it becomes after the first five, ten and fifteen pounds come off.
• TDEE CalculatorHow many calories you burn in a day, from the Mifflin-St Jeor equation and an activity multiplier, with cut and bulk targets beside it.
• BMI CalculatorBody mass index from height and weight in either metric or US units, with the CDC category cut-offs.
• Macro CalculatorGrams of protein, carbohydrate and fat from a calorie target and a diet split. With protein per kilogram, the number a split is judged on.
• Calories Burned CalculatorEnergy burned by an activity from its MET value, body weight and duration. Net of what you would have burned sitting still, which trackers leave in.
• BMR CalculatorBasal metabolic rate from the Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle equations at once, with the disagreement between them shown.

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