Free tool
Weight loss calculator UK: how long will it take?
Work out your daily calories, a safe pace and a realistic date to reach your target weight. Use stone and pounds or kilograms.
Your numbers
Enter your details and your target weight. You get your daily calories, how long it should take, and a starting split of protein, carbs and fat.
An estimate, not medical advice. Nothing you type is sent anywhere.
How it works
How the weight loss calculator works
1. Your resting burn (BMR)
Your body burns calories just to keep you alive. The calculator estimates this with the Mifflin-St Jeor equation, using your sex, age, height and weight.
2. Your daily burn
That number is multiplied by an activity factor, from mostly sitting to very active, to give the calories you burn in a normal day.
3. A safe gap
To lose fat you eat a little less than you burn. About 7,700 calories is roughly 1 kg of body fat, so a gap of about 550 calories a day is around 0.5 kg a week. CHECK against nhs.uk
Built-in safety limits
- The pace is kept between 0.25 and 1 kg a week.
- The daily gap never goes above 25% of what you burn.
- Calories never drop below 1,200 (women) or 1,500 (men and anyone who prefers not to say).
- If your target is below a healthy weight for your height, the plan is built on the lowest healthy weight instead.
- No plan is given if you are under 18, pregnant or breastfeeding, have diabetes or take weight-affecting medicine, have had an eating disorder, or are unwell.
Timeline
How long will it take to lose weight?
It depends on how much you want to lose and how steady you can be. As a worked example, someone who needs to lose 14 kg at a steady 0.5 kg a week needs about 28 weeks. Over the first 12 weeks that's roughly 6 kg.
That surprises people. Most of us hope for faster, but a slower pace is easier to hold, keeps more muscle and is more likely to stay off. The calculator shows an honest timeline with a date, so you can plan for it.
Progress is never a straight line. Water, salt, hormones and training all move the scale. Look at the trend over a few weeks, not one morning.
Questions
Weight loss calculator questions.
How many calories should I eat to lose weight?
It depends on your size, age and activity. The calculator works out your daily burn and takes a safe gap off it, but it never goes below 1,200 calories a day for women or 1,500 for men.
How fast is it safe to lose weight?
A steady pace of about 0.5 to 1 kg (1 to 2 lb) a week is the range usually recommended in the UK. CHECK against nhs.uk The calculator caps the gap at a quarter of what you burn.
How accurate is a weight loss calculator?
It gives an estimate, not a promise. The formulas use averages, so your real result will differ. Weigh in weekly, and if your weight isn't moving after two to three weeks, adjust.
Why does weight loss slow down?
As you get lighter your body burns slightly less, and water and food in your gut move the scale from day to day. That's why the timeline here is "about", not exact.
Who should not use this calculator?
It's for adults only. Don't use it if you're pregnant or breastfeeding, have diabetes or take medicine that affects weight or appetite, have had an eating disorder, or are unwell. Speak to your GP first.
Does exercise change the result?
Yes. The activity setting raises your daily burn. Strength training also helps you keep muscle while you lose fat.
Want someone to do this with you?
Vicky lost weight herself and has coached people for 8 years. Home Grown gives you pre-recorded sessions and food and meal advice, with your numbers built in.
See the coaching