Calorie Calculator
A calorie calculator built on Mifflin–St Jeor: your maintenance number, the BMR under it, and loss or gain targets at 250 and 500 kcal, plus a date if you name a goal weight.
Maintain your weight
Below the guideline floor
The targets
Where that weight sits
Activity level
Units
Switching converts what is already typed — the figures never change because of the units they are shown in.
Sex
The equation carries a different constant for each: + 5 male, − 161 female.
Weekly pace
Optional. Name a weight and this works out how long the pace you pick would take.
Torn between two, take the lower one — the level you pick already counts your training, which is why logging a workout in a food app and eating it back counts the same effort twice.
The four terms, on this body
Mifflin–St Jeor, and no formula picker.Fitted on 498 healthy adults aged 19 to 78 (1990), it predicted resting energy within 10% of measured for more people than any other equation tested (Frankenfield 2005), so it is the one equation this page uses.
How to use
- Pick Metric or Imperial under Units. Switching converts what you have already typed, so the figures never move because of the units, and the choice is remembered on this device.
- Fill in Age and choose Male or Female. Both go straight into the equation, and every year of age takes 5 kcal off your resting number.
- Pick an Activity level. The five chips multiply your BMR by 1.2, 1.375, 1.55, 1.725 and 1.9, each showing the figure it would give, and the page starts you on 1.55.
- Read the figure at the top: maintenance is the one to plan around, and the targets under it are that figure with 250 or 500 kcal taken off or added on.
- Optionally put a Goal weight in and choose Mild or Standard pace to get a week count, a calendar date and the daily calories implied by that pace.
- Re-run it once a few kilograms have shifted. Each kilogram you lose knocks 10 kcal off your BMR, so a 5 kg loss moves the moderate maintenance figure down by about 78.
Where the numbers come from
Age, sex, height, weight, activity. Five inputs, and the calorie calculator turns them into one figure and the five targets around it: what it takes to hold your weight steady, the resting number underneath that, and four targets for shedding or adding a quarter or half a kilogram a week. At the settings the page opens on, a 30-year-old man of 70 kg and 175 cm training three to five days a week needs 2,556 kcal to stay where he is. Lying still for the entire day, he would still burn 1,649 of them.
Each of the five activity levels is a chip that carries what that same body would need at that level, from 1,979 kcal sedentary to 3,133 very active. A spread of over a thousand calories from one choice catches most people out, which is why it is printed on the chips rather than hidden behind them. A BMI meter reads the height and weight you already entered, and three closed explainers say what each level means, who the BMI bands are for and where the figure comes from.
Ten weeks to 65 kg
Take the page exactly as it loads: male, 30 years old, 70 kg, 175 cm, moderately active. Maintenance comes out at 2,556 kcal and the 0.5 kg per week loss target reads 2,056. Type 65 into Goal weight, leave Pace on Standard, and the line underneath works out at about 10 weeks, gives the date ten weeks from today, and repeats the 2,056 kcal a day it would take.
Now switch Sex to Female and touch nothing else. Maintenance drops to 2,298. The equation carries a constant of +5 for men and -161 for women, a gap of 166 kcal before you move at all, which the 1.55 activity multiplier stretches to about 257.
Good to know
- The equation was fitted to population averages, so it does best on an average body and worst at the edges. A heavily muscled person will be told to eat less than they actually need.
- Activity multipliers are blunt instruments. One number covers everyone who trains three to five days a week, whether that means easy swimming or heavy intervals, and the real uncertainty around any TDEE estimate is wider than the 250 kcal gaps between the targets.
- The goal projection is a straight line rounded up to whole weeks. It has no model of plateaus, holidays, water weight, or the way maintenance falls as you get lighter.
- In imperial the goal weight and both paces read in pounds: Mild is 0.55 lb a week and Standard 1.1 lb, the same 0.25 and 0.5 kg underneath, so a projection never mixes units.
- A loss target under the floor of the 2013 AHA/ACC/TOS guideline (1,200 kcal a day for women, 1,500 for men) is tagged and explained, but nothing else checks whether a target suits you. The equation was fitted on adults 19 to 78, so a younger age gets a caution, and pregnancy, breastfeeding or a thyroid condition sit outside what any of this models.
Frequently asked questions
How many calories should I eat to lose weight?
Take your maintenance figure and subtract. The Weight loss target cuts 500 kcal a day for roughly half a kilogram a week, and Mild loss cuts 250 for half that pace. At the page defaults those two read 2,056 and 2,306 against a maintenance of 2,556.
What's the difference between BMR and TDEE?
BMR is what you would burn doing absolutely nothing, keeping your heart, lungs and organs running. TDEE is that figure multiplied by an activity factor to cover moving, working and training. On this page the row marked At rest is your BMR and the figure at the top is your TDEE.
Which activity level fits a desk job plus three gym sessions a week?
Moderately active, the 1.55 multiplier the page opens on. Sedentary means genuinely no exercise, Lightly active covers one to three sessions, Active is six or seven, and Very active is hard daily training or heavy manual work. Torn between two? Take the lower one.
Why Mifflin–St Jeor rather than Harris–Benedict?
It is the newer equation and it validates better against modern populations, which is why most clinical references reach for it first. Katch–McArdle can beat both when you know your body-fat percentage, since it works from lean mass, though that is a measurement most people do not have to hand.
Do I add my workout calories on top of this?
Usually you should not, because the activity level you chose already has them baked in. Picking Moderately active covers those gym sessions once. Logging them again in a food app and eating them back counts the same effort twice, which is the commonest way a careful deficit quietly disappears.
Where does the 7,700 calories per kilogram rule come from?
Body fat stores roughly 7,700 kcal per kilogram, about 3,500 per pound. Seven days at a 500 kcal deficit makes 3,500, which is where the classic pound-a-week figure came from. It holds reasonably well early on and drifts later, since part of what you lose is water and lean tissue rather than fat.
My goal date looks too good. Should I trust it?
Read it as arithmetic. The projection divides the weight you want to shift by the pace you picked and rounds up to whole weeks, so 5 kg at half a kilo a week is exactly 10 of them. Real timelines run longer because adherence wobbles and your maintenance number keeps falling.
Why is there a BMI meter on a calorie page?
The same height and weight answer both questions, and the answers are different in kind. Calories tell you what to eat; BMI tells you where your weight sits against the WHO bands. Its card reads your age too, so put in anything under 20 and it says that children and teens are scored on percentiles instead.
Missing something in Calorie Calculator? Suggest a feature →
Tell someone who needs this.