How to work out your maintenance calories

Step one: estimate with a formula

The Mifflin-St Jeor equation is one of the more reliable formulas for estimating resting energy use in most adults. It uses weight in kg, height in cm and age in years:

• Men: (10 x weight) + (6.25 x height) minus (5 x age) + 5
• Women: (10 x weight) + (6.25 x height) minus (5 x age) minus 161

That gives your resting figure. Multiply it by an activity factor to estimate your total: about 1.2 if you mostly sit, 1.375 if you are lightly active or train two or three times a week, 1.55 if you train most days, and 1.725 for physical jobs or hard daily training.

Take a 45-year-old woman who weighs 80 kg, is 165 cm tall and trains three times a week. Her resting estimate is 800 + 1,031 minus 225 minus 161, which is roughly 1,445 kcal. Multiplied by 1.375, her estimated maintenance is around 2,000 kcal a day.

Why formulas are only a starting point

Formulas are built from averages. Two people of the same age, height and weight can differ by a few hundred kcal a day because of muscle mass, genetics and, above all, how much they move outside the gym. Someone who spends the day on their feet in a warehouse and someone at a desk in Salford Quays will not burn the same, even if they both do three classes a week.

Fitness trackers and smartwatches are handy for spotting trends in activity, but their calorie estimates vary widely between devices. Use them to see whether you moved more or less than usual, not as an exact figure to eat to.

Step two: refine it with your own data

This is where you find your real number. It takes two to three weeks and relies on honest tracking.

1. Eat as normal but log everything, including drinks, cooking oil and sauces. A kitchen scale makes a big difference, and our guide to tracking calories without obsessing has practical tips.
2. Weigh yourself each morning after the toilet and before food or drink, then work out a weekly average.
3. Keep your activity roughly steady during the test, including your usual daily step count.
4. At the end, compare your average daily intake with the change in your weekly average weight.

If your weight was flat, your average intake is close to maintenance. If you lost about 0.5 kg a week, add roughly 550 kcal to your average intake, since half a kilo of fat holds around 3,850 kcal spread over seven days. If you gained, subtract in the same way.

Ignore the first week if you have just changed how you eat, because shifts in water and stored carbohydrate can skew it. Our guide on why the scales go up and down explains those swings.

Where people go wrong

The tracking method only works if the data going in is honest. These are the usual errors.

• Changing how you eat during the test. Many people eat better the moment they start logging, which measures a diet rather than their normal intake. Fine, as long as you know which one you are measuring.
• Guessing portions. Eyeballed pasta, cereal and peanut butter are routinely under-recorded. Weigh them for the test period, even if you stop afterwards.
• Using too short a window. One week is easily skewed by water, a salty meal or your menstrual cycle. Two to three weeks smooths that out.
• Comparing single weigh-ins. Monday to Monday can mislead. Compare one week's average with the next week's average.

Your maintenance figure will never be perfect, and it does not need to be. Getting within 100 to 200 kcal is plenty to set a deficit that works.

Keeping the number up to date

Maintenance falls as you lose weight, because a lighter body costs less to run and to move. It also drops if your daily movement quietly falls, which is common when people diet. Recheck your numbers every six to eight weeks or after every 4 to 5 kg lost.

Your step count is one of the biggest variables you control. Keeping it steady makes your maintenance far more predictable, which is why coaches keep going on about it. See steps and NEAT for simple ways to keep it up on busy days.

Life changes shift it too. A new desk job after years on your feet, an injury that stops you walking, or starting to train for a first HYROX can all move maintenance by hundreds of kcal a day. Whenever your routine changes, run the tracking test again rather than guessing.

Using maintenance to set your target

Once you have a reliable figure, setting a fat loss target is simple. Take 15 to 25% off for a moderate deficit, which our guide to the calorie deficit explains in more detail. Set protein at 1.6 to 2.2 g per kg of body weight a day, then fill the rest with a mix of carbs and fats you enjoy.

Knowing your maintenance is also what lets you finish a diet well. When the fat loss phase ends, you move back up to this number rather than guessing. If you want a coach to go through your numbers with you, the Lycan Strength free trial includes a complimentary fitness assessment.