How Many Calories Should I Eat Per Day? (Calculator Guide 2026)

As a rough average, adult women maintain their weight on about 1,600–2,400 calories a day and adult men on about 2,000–3,000, but your own number comes from your body and your week: estimate your BMR with the Mifflin-St Jeor equation, multiply it by your activity factor to get your TDEE, then subtract 300–500 calories to lose weight or add 200–300 to gain lean muscle. That gives you a genuinely good starting point in two minutes. This guide shows the exact math, worked examples and a table by age and activity, then explains why the number drifts after a few weeks and how adaptive tracking learns your real expenditure from the meals you log and your weigh-ins.

Shortcut: the interactive calorie calculator runs the formulas below for you — maintenance, target and macros, instantly.

The Two-Minute Calculation, in Three Steps

Your daily calorie target comes from three quick steps: estimate the energy your body burns at rest (BMR), scale it up for your activity level (TDEE), then adjust for your goal. Let us go through each.

Step 1: Calculate Your BMR (Mifflin-St Jeor)

Your Basal Metabolic Rate is the number of calories your body burns just to keep you alive at complete rest — breathing, circulating blood, maintaining body temperature. It is the single largest chunk of your daily energy use, typically 60 to 70 percent of the total.

The most widely used and reliable estimate is the Mifflin-St Jeor equation, which nutrition professionals generally consider the most accurate of the common formulas for the general population. It uses metric units (kilograms and centimetres):

The only difference between the two versions is the final constant (+5 for men, −161 for women), which reflects average differences in body composition. Enter your numbers and you have your BMR — the floor of your daily energy needs.

Step 2: Multiply by Activity to Get Your TDEE

Nobody spends the whole day lying still. Your Total Daily Energy Expenditure (TDEE) is your BMR scaled up to account for movement: walking, working, exercising, even fidgeting. You estimate it by multiplying your BMR by an activity factor.

Most people overestimate here. Three gym sessions a week plus a desk job is "lightly" to "moderately" active, not "very active." When in doubt, pick the lower multiplier — it is easier to add calories later than to discover you have been overeating for a month.

Step 3: Adjust for Your Goal

Your TDEE is your maintenance level — the intake that keeps your weight roughly stable. From there you nudge up or down depending on what you want:

• Lose weight: subtract 300–500 calories per day. That produces roughly 0.25–0.5 kg (about 0.5–1 lb) of loss per week — a rate that is sustainable and mostly protects muscle.
• Maintain weight: eat at your TDEE.
• Gain lean muscle: add 200–300 calories per day. A modest surplus supports muscle growth while limiting fat gain; large "bulk" surpluses mostly add fat.

Worked Examples

Formulas are abstract until you see them run. Here are three realistic profiles from start to finish.

Notice how different three "normal" people are: from about 1,525 to nearly 3,000 calories a day. This is exactly why a single number from a generic article is close to useless — your target depends on your body, your activity, and your goal.

How many calories do I need a day? Table by sex, age and activity

If you want a number before doing your own arithmetic, this table runs the Mifflin-St Jeor equation from Step 1 for two reference adults and multiplies by three of the activity factors from Step 2. The reference bodies are assumptions, not population averages: a woman of 162 cm and 65 kg, and a man of 175 cm and 80 kg. The equation weighs 10 kcal per kilogram and 6.25 kcal per centimetre, so every 5 kg you differ from the reference moves the BMR by 50 kcal and every 8 cm by 50 kcal, before the activity multiplier is applied. Read the rows as the shape of the terrain, not as your coordinates on it.

One row worked in full, the 35-year-old woman: BMR = (10 × 65) + (6.25 × 162) − (5 × 35) − 161 = 650 + 1,012.5 − 175 − 161 = 1,326.5 kcal. Sedentary: 1,326.5 × 1.2 = 1,591.8, shown as 1,590. Moderately active: × 1.55 = 2,056.1, shown as 2,060. Very active: × 1.725 = 2,288.2, shown as 2,290. Every maintenance cell is rounded to the nearest 10 kcal.

These are maintenance figures. The weight-loss target for any row is that row minus 300–500 kcal, with the 1,200 and 1,500 kcal floors from the warning box above still applying: a sedentary 65-year-old woman at 1,410 kcal has only about 200 kcal of room before she reaches the floor, which is exactly the case where a smaller deficit plus more movement beats a larger deficit. The gap between the woman and the man of the same age is 397 kcal at rest, and the equation shows where it comes from: 150 kcal for the 15 kg difference, 81 kcal for the 13 cm, and 166 kcal from the two constants (+5 against −161). Change the reference bodies and the gap changes with them, which is why a table can only ever be the starting point the rest of this article describes.

For your own height, weight and age, the calorie calculator returns maintenance, a target and macros in one pass, and the TDEE calculator shows all five activity levels side by side.

Why Your Calculated Number Stops Working After a Few Weeks

Here is the part most calculators never mention. That tidy number you just computed is accurate on the day you compute it — and then it quietly drifts out of date. Three forces push it off:

1. Your body adapts

When you eat in a deficit, your body defends itself. Non-exercise movement drops, hormones shift, and you burn fewer calories than the formula predicts — a well-documented effect called metabolic adaptation. Research suggests this adaptation can be meaningful over weeks of dieting, so the deficit you started with slowly shrinks even if your eating never changes.

2. A smaller body burns fewer calories

BMR is tied directly to body weight in the Mifflin-St Jeor equation. Lose 5 kg and your maintenance level genuinely falls. The 1,525-calorie target that produced steady loss in week one can quietly become your maintenance level by week eight — and the scale stalls even though you are "doing everything the same."

3. Tracking drift

Portion estimates creep. Untracked bites, oils, dressings, and "close enough" logs accumulate. Over a few weeks, a real 400-calorie deficit on paper can become a 100-calorie deficit in reality — barely enough to see on the scale.

The result is the classic plateau: you feel like you are following your target perfectly, yet progress stops. Static calculators cannot see any of this, because they hand you one number and walk away. We go deeper on this in why static calorie counters fail, and on the fix in our breakdown of the adaptive energy expenditure algorithm.

How PlateLens Keeps Your Number Honest

A good calorie target is a moving target, and PlateLens is built to move with you. The formula above gives you a strong day-one number; from there, PlateLens learns from your logs and weigh-ins and suggests new targets as your body changes:

• Your starting point, calculated for you. During onboarding, PlateLens runs the same BMR and TDEE math above from your height, weight, age, activity, and goal — so you skip the arithmetic and start with a solid target.
• Your real expenditure, learned every week. Turn on Adjust with my logs and weigh-ins once, and the adaptive energy expenditure algorithm works out, every week, the expenditure that fits the meals you log and the way your weight moves. When metabolic adaptation or a lighter body lowers what you burn, your dynamic expenditure follows it. Already logging and weighing in? Your first dynamic expenditure can arrive shortly after you switch it on.
• Steady, trustworthy steps. Each Sunday’s update moves your dynamic expenditure by up to 5%, following the trend of up to three weeks of weigh-ins, so one unusual morning on the scale barely moves it. A week with gaps keeps your last dynamic expenditure, and the next week with enough data picks up right where it left off.
• New targets, suggested as you progress. Every 14 days, PlateLens checks your targets against your latest expenditure and weight and, whenever your progress calls for it, suggests new calorie and macro targets built for where you are now. A quick check-in on Home shows where the number comes from, and one tap on Apply New Targets puts them to work. Change your goal, from losing weight to maintaining or from cutting to lean gaining, and PlateLens recommends matching targets right away.
• Your own lab result, if you have one. Had a resting metabolism test, such as indirect calorimetry? Enter the result once and PlateLens builds your expenditure on your own measured resting energy from that day on.
• A coach that knows your numbers. Ask the AI coach about your expenditure and it knows which source you use and how your weekly learning is going, and explains any change in plain language.

The dynamic expenditure and the target suggestions are free on every plan, on iPhone, Android and the web. And because an adaptive expenditure is only as accurate as the food log it learns from, PlateLens learns from the most accurate one: in its published validation study, the Dietary Assessment Initiative measured PlateLens at ±1.1% calorie error across 180 weighed meals, and the open-source Foodvision Bench reproduced that result on 231 more meals on its public GitHub leaderboard.

The Bottom Line

You can absolutely answer "how many calories should I eat a day" in two minutes: estimate your BMR with Mifflin-St Jeor, multiply by an honest activity factor, and adjust 300–500 down to lose or 200–300 up to gain. That gives you a genuinely good starting point — better than any generic number online.

Just remember that it is a starting point. Your body will adapt, your weight will change, and your logging will drift, so the number that works today will need adjusting in a few weeks. The people who succeed long term are not the ones who calculate the perfect number once — they are the ones who keep it accurate over time. That is the whole reason adaptive tracking exists: it learns what you really burn and keeps your target in step with you.

Logging That Keeps Your Deficit Real

Tracking drift is the force you meet at every meal: a 400-calorie deficit on paper can shrink to 100 in reality as portions creep and oil goes unlogged. PlateLens logs the meal from a photo or from a sentence you would actually say, such as “turkey meatballs, a cup of couscous and a green salad with dressing”, and takes corrections in plain words: “the couscous was closer to a cup and a half.” With weekly learning on, each meal you log also feeds your dynamic expenditure, so every accurate entry carries into the targets PlateLens suggests. The Dietary Assessment Initiative measured PlateLens at ±1.1% calorie error across 180 weighed meals in its published validation study, and the open-source Foodvision Bench reproduced it on 231 more on its public GitHub leaderboard.

Frequently Asked Questions