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Calorie deficit calculator

Get a rough idea of how many calories you burn in a day, pick a sensible target a little below that, then jot down what you eat today and see what’s left.

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.

Today’s food

Set a target above to see what’s left for today.

Search foods

Type at least two letters. UK foods and supermarket brands.

Add a food by hand

Eaten so far

Nothing added yet.

Saved only in this browser on this device. It clears itself tomorrow.

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

Want to keep your diary across days?

This page forgets everything tomorrow. Save your diary across days with a membership: the Food Diary/Calorie Calculator keeps every day, scans barcodes and sits alongside your training plan, workout log and 225 recipes. It’s £79 a year, all taxes included.

See the membership 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.
Through the day, search for what you eat or add it by hand. The total and what’s left update as you go, and you can edit or remove anything.
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.

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. 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 my food log saved or sent anywhere?

No. The log is kept only in your browser on this device, under the name ffc_cdc_day. It isn’t sent to us, you don’t need an account, and it clears itself the next day or when you press Reset the day.

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.