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Calorie deficit calculator

Get a rough idea of how many calories you burn in a day and pick a sensible target a little below that. Then try the food log demo: a sample day is already filled in, so you can see how what’s left works.

Your daily target

All fields are optional. Fill in what you’re happy to share for an estimate, or skip to typing your own target.

Try the food log: a sample day

This is a demo. We’ve filled in a typical day with a sample 1,800 kcal target; use your own target above if you like. Edit or remove the sample foods, and add up to 3 of your own.

540 kcal left

Eaten 1,260 of 1,800 kcal target (sample target)

Eaten so far

Porridge made with semi-skimmed milk40 g oats, 200 ml milk · sample
250 kcal
Tuna and sweetcorn sandwich1 sandwich · sample
390 kcal
Apple1 medium · sample
60 kcal
Chicken stir-fry with rice1 plate · sample
560 kcal

Demo: you can add 3 more foods. Edit or remove the sample foods as you like.

Search everyday foods (demo)

Type at least two letters. The demo searches about 2,850 everyday foods; members search over 52,000 UK foods and supermarket products.

Add a food by hand

The demo isn’t saved anywhere. Reload the page and it goes back to the sample day.

Sample and food values are typical estimates from McCance and Widdowson’s CoFID (Open Government Licence) and Open Food Facts (ODbL). Check the label if it matters. Credits

Members

The full version is for members

In the member area, the Food Diary/Calorie Calculator does everything this demo does, without the limits:

Log as many foods as you eat, in breakfast, lunch, dinner and snacks, every day
Search over 52,000 UK foods and supermarket products, or look up a barcode (and scan it on phones that support scanning)
Your diary kept across days: go back to earlier days and see the last 7 days at a glance. It’s saved on your device, and in your account too if you choose, so it’s there on your phone and computer
A daily target worked out from your details with the same Mifflin-St Jeor equation, showing how many kcal you’ve got left or how far over you are
Protein, carbs, fat, sugars and salt for the day, alongside the calories
Saved meals, your own foods, and one-tap adding from the recipes and meal plans
Download your diary as a spreadsheet file (CSV), or delete it, at any time

All the figures are estimates for general guidance, in the member area too. It sits alongside 13 training plans, the workout log and 225 recipes, for £79 a year, or £9.99 a month on a 12-month plan, all taxes included.

Join FitFitCity How the Food Diary works

What is a calorie deficit?

Your body uses energy all day, even when you’re asleep. A calorie deficit just means eating a bit less energy than you use, so your body makes up the difference from its own stores. Over weeks, that’s what moves the scales.

You don’t need a huge gap. Cutting hard is tough to keep up, and it’s easy to slide back. A modest, steady deficit you can live with usually beats a dramatic one you can’t.

How to use the calculator

Fill in your age, height, weight and how active you are. Use cm or ft and in, and kg or stones and pounds, whichever you think in.
Pick a deficit. 300 kcal is gentle, 500 kcal is steady. Press Work out my target.
Prefer your own number? Type it into the own target box instead.
Try the food log demo below the target. A sample day is already filled in: edit or remove foods, add up to three of your own, and watch the total and what’s left update. Members can keep a full diary every day.
Give it two to four weeks before you judge it. If your weight hasn’t shifted, trim another 100 to 200 kcal (staying above the minimums below); if you’re always starving, ease off.

How we work out your numbers

First we estimate the energy your body uses at rest with the Mifflin-St Jeor equation:

Men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5
Women: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161
If you’d rather not say, we use the halfway point between the two

Then we multiply by an activity factor, from 1.2 if you’re mostly sitting to 1.9 if you have a physical job and train as well. That gives your estimated maintenance calories, rounded to the nearest 10. Your target is maintenance minus the deficit you pick, but never below about 1,200 kcal a day for women or 1,500 kcal a day for men (and 1,500 if you’d rather not say).

As an example, a 35-year-old woman who is 165 cm, weighs 70 kg and is lightly active comes out at about 1,920 kcal for maintenance, so a 500 kcal deficit gives a target of about 1,420 kcal.

Questions

How big should my calorie deficit be?

For most adults we suggest starting 300 to 500 kcal a day below your estimated maintenance. A smaller gap is easier to stick to week after week, and you can always adjust it once you’ve seen how your weight moves over a few weeks.

How accurate is the calculator?

It’s an estimate. The Mifflin-St Jeor equation is widely used, but real people can burn noticeably more or less than it predicts, and food labels and portion sizes vary too. Treat the number as a starting point, then adjust based on how you get on over two to four weeks.

Why won’t it go below 1,200 or 1,500 kcal?

We never suggest less than about 1,200 kcal a day for women or 1,500 kcal a day for men (and 1,500 if you’d rather not say). If your numbers would take you lower, we stop there and suggest you speak to your GP first. The same applies if you type in your own target below these levels.

Is anything I type saved or sent anywhere?

No. Your numbers are worked out in your browser, and the food log demo isn’t saved at all: nothing goes into cookies or browser storage, and nothing you type is sent to us. Reload the page and it goes back to the sample day.

What’s the difference between this and the members’ version?

This page is a demo of the food log: a sample day you can edit, with room for three more foods and a search of about 2,850 everyday foods. Members get the full Food Diary/Calorie Calculator, with as many foods as they eat, over 52,000 UK foods and supermarket products, barcode look-up, a diary kept across days, a daily target with kcal left or over, and protein, carbs, fat, sugars and salt.

Can I use it if I’m under 18, pregnant or have a medical condition?

Please don’t use it to cut calories if you’re under 18, pregnant or breastfeeding, have or have had an eating disorder, or have a medical condition. Speak to your GP, and see the NHS pages linked below for advice that fits you.