UK weight-loss calculator
Weight loss by date calculator
Most people do not start with a goal weight. They start with a date: a holiday, a wedding, the first of January. This estimates what could come off by then.
Updated
I am , aged . I weigh st lb and I am cm tall. I am . I want to know how much I could lose by , going at a pace.
4blanks still to fill
Everything is worked out in your browser. Your measurements are never sent anywhere, and the date is not stored with them.
Fill in the sentence above and pick a date, and this will estimate the range that could come off by then.
What the range means
- The headline range
- The span between a favourable and an unfavourable set of assumptions about how closely a plan is followed and how much energy expenditure adapts. Not a best case and a worst case, and not a promise: the honest width of the estimate.
- Weight then
- What your weight would be at each end of that range on the date you picked.
- Daily calories
- The intake behind the pace you chose, after the same safety floors the rest of the site applies. It is the amount to eat, not a target weight.
- Middle estimate
- The central assumptions on their own, for when a single number is more useful than a span. It carries no more authority than the range around it.
A date does not change what is possible
Picking a nearer date does not make faster loss safe, and this calculator will not pretend otherwise. The pace is capped the same way everywhere on this site, so a tight deadline produces a smaller number rather than a more aggressive plan.
How is this calculated?
This is the same weekly simulation as the main weight loss calculator, asked the other question. That one runs until you reach a target weight and reports how long it took. This one runs until the date you picked and reports where you would be.
Each week it recalculates your basal metabolic rate at your new weight using the Mifflin-St Jeor equation[American Journal of Clinical Nutrition], multiplies it for your activity level, and takes off the deficit implied by your chosen pace. Because a lighter body needs less energy, the same intake produces a shrinking deficit, so the curve flattens rather than running in a straight line.
Where it stops early
- At the healthy weight range. A forward projection has no goal weight to protect it, so left alone it would happily carry on past a healthy weight and print the result. It stops at the bottom of the healthy BMI range for your height and says that is what it did.
- At a plateau. Hold one intake long enough and the deficit closes on its own. Where that happens before your date, the estimate reflects it rather than assuming loss continues forever.
The pace options, the calorie floors and the weekly ceiling are the same ones used everywhere else on the site, and all of them are written out on the methodology page, including the parts we are least certain about.
What this cannot tell you
The pace options here sit inside the range the NHS describes as a safe rate of loss, 0.5 to 1 kg a week[NHS], and the calorie figure behind them is your estimated maintenance less the deficit that pace implies[NHS Better Health]. Beyond that, the further away the date, the less any model of this kind is worth. These are estimates built on population averages, and they cannot account for:
- How your own metabolism differs from the equation average, which between individuals is substantial.
- Water weight, which usually makes the first fortnight look faster than any steady model predicts.
- Anything that happens between now and then: illness, a holiday, a change of job, a stretch where none of it is a priority.
- Medication and health conditions, including thyroid disorders and PCOS.
- Whether the pace you picked today is one you will still be following in three months.
A deadline is a poor motivator on its own
A date is useful for picturing what is realistic. It is less useful as something to hit at any cost. If the number this returns is smaller than you hoped, the useful response is usually a longer horizon rather than a harder deficit.
Related calculators
Frequently asked questions
How much weight can I lose by Christmas?
It depends on how far away Christmas is and what you weigh now, which is what the calculator above is for. As a rough guide, at the pace the NHS describes as safe, a person loses somewhere between about half a kilogram and a kilogram a week, so three months is roughly 6 to 12 kg and a month is roughly 2 to 4.5 kg.
Heavier people tend to lose faster at the start, so the same period produces a bigger number at a higher starting weight. Enter your own figures rather than working from the average.
Why does it give a range instead of a number?
Because the underlying estimate does not support more precision than that. Two people with identical measurements following identical plans do not lose identical amounts. A single figure against a fixed date would look more authoritative and be less honest, so we show the span and say what produces it.
What if I want to lose more than it says by my date?
Then the date is too close for that amount, and the calculator will not manufacture a plan to fit it. Faster paces are capped at the same limits used across this site, so choosing a more aggressive option cannot push the estimate past what is generally considered safe.
The more useful move is usually to keep the pace and move the date, or to treat the date as a checkpoint rather than a finish line.
How far ahead can I set the date?
Up to about eighteen months. Beyond that a projection is not really telling you anything: too much of the answer depends on things nobody can model that far out, and a specific figure for a date two years away would be false precision rather than information.
Do you store my weight or my date?
No. Every calculation runs in your browser. Your measurements are never sent to us and are never included in our analytics. If you come back, your entries are restored from your own device, and "Start again" clears them.
Sources
- Overweight and obesity in adults, NHS
- Calories and weight loss, NHS Better Health
- A new predictive equation for resting energy expenditure in healthy individuals, American Journal of Clinical Nutrition
Important information
The calculators on this site provide general information and estimates. They are not medical advice and they do not diagnose any condition.
Everyone is different, and individual energy needs vary for reasons these equations cannot capture. If you have a health condition, take medication, are pregnant or breastfeeding, or have any concerns about your weight, speak to your GP, pharmacist or a registered dietitian.