Weight Loss Calculator
Compare two safety-floored calorie deficits and see a clearly labelled linear estimate of the time needed to reach a lower target weight.
Results
How many calories should I eat to lose weight?
To lose weight you have to spend more energy than you take in, and this weight loss calculator turns that sentence into two numbers you can act on. It estimates the intake at which your weight would hold steady, subtracts a deficit, and reports the calorie target that results along with how long the gap between your current and target weight would take at that rate.
It is a free weight loss estimator rather than a tracker: the target it gives you is a maintenance figure minus a deficit, reported in kcal a day, and both halves are shown. Working as a lose weight calorie calculator in either unit system, it accepts kilograms and centimetres or pounds, feet and inches, and converts once before any arithmetic runs.
Two scenarios are reported rather than one, because the honest answer to how many calories to lose weight is a range that depends on how fast you are willing to go:
| Scenario | Daily deficit | Approximate rate |
|---|---|---|
| Mild loss | 250 kcal a day below maintenance | About 0.23 kg a week |
| Standard loss | 500 kcal a day below maintenance | About 0.45 kg a week |
Turning a deficit into a timeline
The deficit itself is subtraction: maintenance intake minus what you actually eat. Turning it into weight uses one more constant, the traditional energy density of body mass at 7,700 kcal per kilogram, or roughly 3,500 kcal per pound. If you want to compare a specific intake against maintenance rather than get a timeline, the calorie deficit calculator does that directly.
Worked through: a 500 kcal daily deficit is 3,500 kcal across a week. Divided by 7,700, that is about 0.45 kg a week, and a 250 kcal deficit is about half of it. Run in reverse, a target of 0.5 kg a week implies roughly 550 kcal a day.
The constant is an approximation and this page treats it as one. It assumes every kilogram lost has the same energy content, which is not exactly true, and that the deficit keeps working at full strength, which it does not.
How the timeline is built
This calculator first runs the approved calorie engine twice on the same body and activity inputs: once for a mild loss target and once for a standard loss target. It then compares your current and target weight and divides the gap by the delivered weekly rate from each calorie scenario. The timeline is deliberately labelled linear rather than predictive: as body mass falls, expenditure usually falls too, so real weight loss often slows.
The word delivered is doing real work there. If a deficit would push intake below the published minimum of 1,500 kcal a day for men or 1,200 for women, the target is raised to that floor and the timeline is recalculated from the slower rate the floor actually produces, not the rate the scenario is named for. Where maintenance is already at or below the floor, no deficit can be served safely and the page says so instead of producing a figure.
Why only two loss rates appear
The route shows the mild and standard loss scenarios only. Faster loss targets make the minimum-intake floor more likely to dominate the answer, and this page is meant to compare realistic educational deficits rather than serve an aggressive plan.
Sources and limitations
Sources reviewed 27 August 2026. This page uses the calorie calculator's published minimum-intake floor and labels the result as a planning estimate, not medical or dietary advice. Real weight change is dynamic, and anyone whose safe intake is already at maintenance needs professional guidance rather than a larger deficit from a web tool.
It says nothing about food quality, training, sleep, medication or the many reasons weight does not move in a straight line. A calorie target is one input into losing weight, not a plan.
Frequently asked questions
How long will weight loss take?
This page gives a linear planning estimate from two calorie deficits. Real weight change is dynamic, and the estimate slows when the published minimum-intake floor limits the deficit.
How many calories should I eat to lose weight?
Fewer than you spend, by an amount you can hold. This calculator works out your maintenance intake, subtracts 250 kcal a day for the mild scenario and 500 for the standard one, and reports both targets. Neither is ever reported below 1,500 kcal a day for men or 1,200 for women, so the answer you get is the lower of the deficit you asked for and the floor that applies.
Where does the deficit come from?
Maintenance minus intake. This page estimates maintenance from your body and activity, applies the mild or standard reduction, and reports the target that results. To compare a specific intake figure of your own against maintenance, use the calorie deficit calculator instead.
How is the weekly rate worked out?
The conventional energy density is 7,700 kcal per kilogram of body mass, or about 3,500 per pound. A 500 kcal daily deficit is 3,500 a week, which divided by 7,700 is roughly 0.45 kg a week. This page uses that constant to build the timeline and says plainly that it is an approximation, not a law.
Why does the estimate say it is linear?
Because it divides the weight you want to lose by one constant weekly rate. Real loss is not constant: as body mass falls, the energy needed to carry it falls too, so the same intake becomes a smaller deficit and loss slows. The timeline is labelled a linear estimate rather than a prediction for that reason, and it will tend to be optimistic over long spans.
Is a 500 calorie deficit safe?
For many healthy adults it is a conventional starting point, which is why it is the standard scenario here. It stops being appropriate when the resulting intake falls below the published minimum, and the calculator will not report a target under that floor. If your maintenance is already at or below the floor, there is no deficit this tool can serve safely, and it says so rather than inventing one.
Can I use this during pregnancy or breastfeeding?
No. Pregnancy and breastfeeding change energy needs in ways this calculator does not model, and deliberate weight loss during either is something to plan with a midwife or doctor. It is also not intended for children or adolescents, or for anyone managing an eating disorder or a condition that affects weight or metabolism.