i
Log in a couple of taps.
Scan a UK barcode, search, or photograph the plate. Calories and macros fill in.
kcalThe UK weight loss calculator
Weight loss calculator. How many calories to lose weight.
Type your weight, height, age and how active you are. We work out what you burn in a day, then the daily calories for a steady loss of a quarter or half a kilogram a week.
Sex
The equation uses a different constant for each. Pick the one that matches your body's biology.
Age (years)
Height
Weight
Activity level
When you're between two, pick the lower one and adjust after two weeks of real data.
01Past the number
A target is easy.
Hitting it is the work.
The calorie figure is the simple part. Staying under it day after day is where weight loss is won or lost. NutraSafe sets your target as a line on the diary and counts every meal against it, scanned from a UK barcode, and reads the additives on the pack while it's there.
ii
See the day against your target.
A live total against the deficit you set here, so you know where you stand by dinner.
iii
Weigh in, watch the trend.
The scale jumps day to day. The weekly line tells you whether the deficit is working.
iv
Protein and the rest.
Macros plus 14 vitamins and 13 minerals against the UK NRV, so a lower-calorie week still covers you.
02How the deficit works
The maths
behind the loss.
No trick to it. Eat below what you burn and your body draws on stored fat. The rate depends on the size of the gap.
Work out maintenance
Your BMR from Mifflin-St Jeor, times an activity factor. That's the calories that hold your weight steady.
TDEE = BMR × activitySubtract a deficit
About 7,700 calories sit in a kilogram of body fat. So half a kilogram a week is roughly a 550 calorie daily deficit.
target = TDEE − 550Pick a rate you can keep
0.25kg a week is gentler and easier to sustain. 0.5kg is the common steady rate. Faster usually costs more muscle.
Adjust on real data
The estimate gets you started. Track for two to three weeks and move the target if the scale isn't doing what you expected.
03Frequently asked
Questions
people ask.
Answers sourced to the NHS and the standard energy-balance maths.
How many calories should I eat to lose weight?
Work out your TDEE (the calories you burn in a day), then eat below it. A deficit of about 550 calories a day loses roughly half a kilogram a week, which the NHS treats as a steady, sustainable rate. The calculator gives you the daily figure for your body and activity level.
What is a safe rate of weight loss?
The NHS suggests aiming to lose 0.5 to 1kg (1 to 2lb) a week, through a daily deficit of about 500 to 600 calories. Faster than that usually means losing more muscle and is harder to keep up. Eating below your BMR for long stretches is not recommended.
How is the weight loss calculation worked out?
We use the Mifflin-St Jeor equation for your BMR, multiply by an activity factor for your TDEE, then subtract a deficit for each loss rate. Roughly 7,700 calories sit in a kilogram of body fat, so half a kilogram a week is about a 550 calorie daily deficit. The numbers are a starting point; adjust after two to three weeks of real data.
Why am I not losing weight in a calorie deficit?
The usual reasons are underestimating what you eat, overestimating what you burn, and water retention hiding fat loss on the scales. UK labels are only accurate within 20 per cent, and unweighed portions add more error. Weigh your food for a week, weigh yourself on the same day each week, and watch the monthly trend.
Do I have to count calories to lose weight?
No, but it makes the deficit visible, which is why most people use it for a few months. Managing portions, cutting high-calorie drinks and snacks, and filling up on vegetables, protein and fibre also work. Counting just sharpens the awareness, and you can stop once the habit is in place.
Aaron Keen is the founder of NutraSafe. He built this calculator on the Mifflin-St Jeor equation and the NHS guidance on safe weight loss, and checks the figures against the sources himself. About the research →
You've got the target.
Now eat to it.
Get NutraSafe on the App Store →
Free to download. The food log, the additive flags and 25 entries a day are free. Pro is £3.99 a month or £34.99 a year for unlimited logs, weight and vitamin tracking, AI Coach, workouts and fasting.
iPhone · iOS 17 · Cancel any timekcal