Losing fat and building muscle both live or die on one number: your maintenance calories. This is the exact amount of energy you burn in a normal day, and it is the pivot everything else turns on. Eat below it and weight comes off; eat above it and weight goes on; eat right at it and your weight stays steady. The problem is that "right" is rarely a single round number — it is a range, and this calculator shows you both the point estimate and the band around it.
The engine below uses the Mifflin-St Jeor equation, the resting-energy formula researchers consistently rate as the most accurate for healthy adults, then multiplies that resting figure by an activity factor to reach your Total Daily Energy Expenditure (TDEE). Because real life is noisier than a spreadsheet, the result is also shown as a ±10% estimate band: the research behind these equations typically lands within about 10% of measured metabolic rate, so treating your maintenance as a range rather than a target is the honest way to use it.
How to Use
- Enter your Age in complete years. Maintenance burn drifts down slowly as you get older, so keeping this current matters more than people expect.
- Pick your Sex. The Mifflin-St Jeor equation uses a different constant for men and women, so this switches the resting-energy line correctly.
- Type your Height in centimeters. If you think in inches, multiply by 2.54 first (70 inches is 177.8 cm).
- Enter your current Weight in kilograms. If you use pounds, divide by 2.205 (176 lb is about 80 kg). Weigh yourself in the morning, after the toilet and before breakfast, for the cleanest input.
- Choose your Activity Level honestly. Sedentary is a desk job with almost no exercise; light is walking a few times a week; moderate is structured exercise three to five days; active is hard training most days; very is daily hard training plus a physical job. Picking a higher tier than you actually live will overstate your maintenance and quietly stall your progress.
- Read the result card. The highlighted Maintenance Calories (TDEE) is your daily pivot. The weekly figure multiplies it by seven, and the −10% / +10% lines are the realistic band your true maintenance probably sits inside.
Start by testing one day inside that band and watch the scale for two to three weeks. If your weight is flat, you have found your maintenance. If it trends up, you are above it; if it trends down, you are below it. That feedback loop is how you turn a formula estimate into your personal number.
The Maintenance Calorie Formula
Your resting energy (BMR) comes from the Mifflin-St Jeor equation published in 1990:
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Then your maintenance calories are:
Maintenance = BMR × activity factor
The activity factors are the standard multipliers used across nutrition practice: sedentary 1.2, light 1.375, moderate 1.55, active 1.725, and very active 1.9. For example, a 30-year-old man who is 180 cm tall and weighs 80 kg, with a moderate activity level, gets a resting figure of about 1,700 kcal and a maintenance total of roughly 2,643 kcal per day. Because the predictive error is around 10%, his realistic maintenance band is about 2,379 to 2,907 kcal.
Why the ±10% Band Matters
A calculator gives you a single number, but metabolism is not a single number. Body composition, genetics, sleep quality, stress, NEAT (the unconscious movement outside formal exercise), and even the temperature of the room all change how many calories you actually burn. Two people with the same age, sex, height, and weight can easily differ by several hundred kcal per day.
That is why the result card deliberately shows a range. If your estimate is 2,600 kcal, the bottom of your band (about 2,340) is where a small, safe deficit for fat loss starts, and the top of the band (about 2,860) is where a gentle surplus for lean mass gain begins. Use the middle to hold steady, then let two to three weeks of honest scale data tell you whether to nudge it up or down.
Examples
Example 1 — Finding the pivot. A 30-year-old man, 180 cm, 80 kg, moderately active. The calculator puts his maintenance at about 2,643 kcal/day, or roughly 18,500 kcal per week. He spends two weeks eating 2,600 kcal and his weight does not move — the estimate was spot on, and he now has a confirmed anchor.
Example 2 — The honest band. The same man sees the −10% / +10% lines of roughly 2,379 and 2,907 kcal. Rather than treat 2,643 as law, he uses the band: he tries one fat-loss block at 2,400 kcal and one lean-gain block at 2,850 kcal, letting the scale pick which is closer to his real maintenance.
Example 3 — A less active person. A 25-year-old woman, 165 cm, 60 kg, with a desk job and little planned exercise (sedentary, 1.2). Her maintenance lands near 1,614 kcal/day, about 11,300 kcal per week. Because her activity tier is low, a small slip upward in snacks or takeout can easily push her above maintenance without her noticing — the range on the result card makes that margin visible.
FAQ
What are maintenance calories?
Maintenance calories are the number of calories you would need to eat in a day to keep your body weight exactly where it is, given your age, sex, height, weight, and daily movement. It is the same figure as your Total Daily Energy Expenditure, or TDEE. Eat at maintenance and your weight stays flat over time.
How do I calculate my maintenance calories?
This calculator uses the Mifflin-St Jeor equation to estimate your resting metabolic rate (BMR), then multiplies it by an activity factor from 1.2 (sedentary) to 1.9 (very active). For most healthy adults it is the most accurate published starting point, and the ±10% band shows the realistic uncertainty around that estimate.
Should I eat at my maintenance to lose weight?
No. To lose weight you eat below your maintenance — typically by a moderate 300 to 500 kcal deficit. To gain weight you eat above it. Maintenance itself is the holding pattern: use it as your reference point, then subtract or add calories depending on your goal.
Why is my maintenance estimate just a range?
Metabolism varies between people and across days because of body composition, sleep, stress, spontaneous movement, and genetics. Research on predictive equations shows a typical error of about 10%, so the result card shows a lower estimate (−10%) and upper estimate (+10%) rather than pretending one number is exact.
How long until my maintenance number is accurate?
The calculator gives you a strong starting estimate on day one, but you should confirm it empirically. Eat near the estimate for two to three weeks and track your weight under consistent conditions. If the scale is flat, you have found your real maintenance; if it rises or falls, adjust by about 100 to 200 kcal and retest.
Does muscle change my maintenance calories?
Yes. Muscle tissue is metabolically active, so people with more lean mass tend to burn more calories at rest and during activity than the equation predicts for the same scale weight. If you lift weights regularly, your true maintenance may sit toward the upper end of the band shown on the result card.
Why does activity level change the result so much?
Activity is the largest lever after body size. Moving from sedentary (1.2) to moderately active (1.55) raises your maintenance by roughly 30%, purely through the multiplier. That is why choosing your activity tier honestly matters — overestimating it is the single most common reason a calorie plan fails.
Disclaimer
This maintenance calorie calculator is provided for informational purposes only and is not medical advice. The estimates come from the Mifflin-St Jeor equation and standard activity factors, which are population-level approximations; individual metabolic rate varies and can differ meaningfully from the result shown. This tool is not intended to diagnose, treat, or replace guidance from a registered dietitian, physician, or qualified health professional, especially if you are pregnant, breastfeeding, managing a medical condition, or taking medication that affects weight or metabolism. Always consult a qualified healthcare provider before making significant changes to your diet or activity.