Last updated: 3 August 2026
Reviewed by Jordan Makin, FA Level 2 Football Coach
Daily calorie needs
One input, three numbers you actually need
Most calorie calculators stop at a single maintenance number. This one goes further: the same details you enter also generate your BMI and a maintenance macro split automatically — no second form, because calories, BMI and macros are all part of the same decision about how to eat, not three separate questions.
Which BMR formula does this use, and why
This calculator uses the Mifflin-St Jeor equation, which most dietitians and sports nutrition bodies now treat as the most broadly accurate formula for the general population. Two older alternatives are still worth knowing about:
- Harris-Benedict — the original 1919 formula (revised 1984). Still used in some clinical settings, but tends to run slightly higher than Mifflin-St Jeor for most people.
- Katch-McArdle — factors in lean body mass instead of total weight, and can be more accurate specifically for people who know their body fat percentage and are leaner than average. Requires a body-fat input that most calculators (including this one) don't ask for by default.
If you know your body fat percentage and want a Katch-McArdle-based estimate specifically, that's the one case where this calculator's Mifflin-St Jeor default may run slightly off from a formula built around your actual lean mass.
How the Mifflin-St Jeor equation works
Your Basal Metabolic Rate (BMR) — the calories your body burns at complete rest just to keep your organs running — is calculated using the Mifflin-St Jeor equation, widely regarded by dietitians as the most accurate formula for most people:
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Once BMR is known, it's multiplied by an activity factor to get Total Daily Energy Expenditure (TDEE) — the number that actually reflects how many calories you burn in a normal day including movement and exercise.
| Activity level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2 | Little to no exercise, desk job |
| Lightly active | 1.375 | Light exercise 1-3 days/week |
| Moderately active | 1.55 | Moderate exercise 3-5 days/week |
| Very active | 1.725 | Hard exercise 6-7 days/week |
| Extremely active | 1.9 | Very hard exercise, physical job, or training twice a day |
Turning your number into a plan
Your TDEE number is your maintenance calories — eat this much and your weight should stay roughly stable over time. From there:
- To lose weight: a deficit of 300-500 calories/day below TDEE produces a sustainable loss rate of roughly 0.3-0.5kg (0.7-1lb) per week. Larger deficits speed things up short-term but are harder to sustain and risk more muscle loss alongside fat loss.
- To gain weight/muscle: a surplus of 200-400 calories/day above TDEE, paired with resistance training, supports muscle gain while limiting excess fat gain.
- To maintain: eat at your TDEE number, adjusting as your weight, activity level or goals change over time.
Calorie needs aren't static — they change as you lose or gain weight, as activity levels shift, and with age. Recalculating every few weeks and comparing against your actual weight trend is more reliable than trusting one number indefinitely.
Why formula estimates and real results can diverge
Even validated formulas like Mifflin-St Jeor are population averages — individual metabolic rate can vary by 200-300 calories/day from the formula's prediction due to genetics, muscle mass, hormonal factors, and other individual variation that no formula fully captures. This is normal, not a sign the tool is broken. The formula gives you a solid, evidence-based starting point; your own weight trend over 2-3 weeks is the real-world calibration that tells you whether to adjust up or down.
Top picks compared
| Pick | Product | Best for | |
|---|---|---|---|
| Top pick | MyFitnessPal Premium | Tracks calories and macros against your calculated daily target. Removes guesswork from your TDEE estimate. | Check price → |
| Option | Cronometer Nutrition Tracker | More detailed than most apps—tracks micronutrients. Helps you hit not just calorie targets but nutritional quality too. | Check price → |
| Precision | Acaia Pearl Smart Scale | Scales every ingredient precisely. Removes calorie-counting errors from meal prep and portion control. | Check price → |
As an Amazon Associate we earn from qualifying purchases. Prices shown on Amazon at time of click.
Frequently asked questions
Are these numbers exact?
No — they're well-validated estimates. Track your weight for 2–3 weeks and adjust calories up or down by ~100–200 if your trend isn't matching the goal.
Why do I need to know both BMR and TDEE?
BMR is your baseline (calories at complete rest); TDEE adds your actual daily activity on top. TDEE is the number that matters for setting calorie targets — BMR alone would badly underestimate what an active person needs.
How big a calorie deficit is safe?
Most guidance recommends staying at or above roughly 1,200 calories/day for women and 1,500 for men without medical supervision, and keeping any deficit to 300-500 calories/day below TDEE for sustainable, muscle-sparing weight loss.
Should I eat back the calories I burn exercising?
If your activity level selection already reflects your typical exercise, no — the TDEE number already accounts for it. Only add back extra calories for exercise that's unusually intense or outside your normal pattern.
Why has my weight stalled even though I'm sticking to the numbers?
Weight loss naturally plateaus periodically due to water retention, hormonal fluctuation and metabolic adaptation — a true stall (no movement over 3-4 full weeks despite consistent tracking) usually means TDEE has genuinely dropped as you've lost weight, and it's worth recalculating.