What is the most accurate calorie formula?

The Mifflin-St Jeor equation (1990) is considered the most accurate for most adults. A 2005 study in the Journal of the American Dietetic Association found it predicted resting metabolic rate within 10% for about 82% of participants — better than Harris-Benedict. The UK's NHS and WHO use the Schofield equation, especially for clinical nutrition and children.

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep you alive. TDEE (Total Daily Energy Expenditure) multiplies your BMR by an activity factor to estimate actual daily calorie needs. TDEE is what you eat to maintain your weight; eating below TDEE causes weight loss.

How many calories do I need to lose 1 kg per week?

One kilogram of body fat contains approximately 7,700 calories. To lose 1 kg per week, you need a deficit of 7,700 ÷ 7 = 1,100 calories per day. Most health authorities (NHS, CDC) recommend a maximum deficit of 500–1,000 calories/day for safe, sustainable weight loss of 0.5–1 kg per week.

Does the UK NHS use a different calorie formula than the US?

Yes. The UK NHS primarily uses the Schofield equation (1985) for clinical nutrition assessments, particularly for hospitalized patients and children. The US uses Mifflin-St Jeor as the preferred formula in clinical dietetics. Both equations give similar results for most adults, typically within 5–10% of each other.

🇺🇸 Mifflin-St Jeor 🇬🇧 UK NHS Schofield 🌍 WHO Standard Harris-Benedict

Calorie Calculator

Your daily calorie needs depend on your BMR (Basal Metabolic Rate) and activity level. Different countries use different formulas — US dietitians prefer Mifflin-St Jeor, while the UK's NHS and WHO rely on the Schofield equation.

Quick Answer

Average adult needs 2,000–2,500 kcal/day (women ~2,000, men ~2,500 — NHS/CDC estimates). Multiply your BMR by your activity factor: 1.2 (sedentary) to 1.9 (very active) to get your TDEE. 1 kg body fat = 7,700 kcal; 1 lb = 3,500 kcal.

Gender

Age

Weight (kg)

Height (cm)

Activity Level

Formula

Which Formula Should You Use?

All three equations estimate your BMR from the same inputs (age, weight, height, sex), but were derived from different population studies:

Formula	Used By	Best For	Accuracy
Mifflin-St Jeor (1990)	US dietitians, fitness apps	General adult population	★★★★★ Most accurate for adults
Harris-Benedict (1990 rev.)	Legacy clinical use	Adults, widely known	★★★★☆ Good but slightly high
Schofield (1985)	UK NHS, WHO, FAO	Children, clinical nutrition	★★★★☆ Best for clinical use

Activity Level Multipliers

The Harris-Benedict activity multipliers are widely used internationally, though some countries prefer slightly different breakdowns. The UK NHS often uses a simplified 3-level classification for clinical settings.

Level	Multiplier	Description
Sedentary	1.2×	Desk job, little or no exercise
Lightly Active	1.375×	Light exercise 1–3 days/week
Moderately Active	1.55×	Moderate exercise 3–5 days/week
Active	1.725×	Hard exercise 6–7 days/week
Very Active	1.9×	Physical job + twice-daily training

Calorie Targets for Common Goals

1 kg of body fat ≈ 7,700 calories. To lose 0.5 kg/week, eat 550 cal/day below TDEE. Most health bodies (NHS, CDC, WHO) recommend not going below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.

Frequently Asked Questions

Are calories the same worldwide?

Yes — the calorie (specifically the kilocalorie, "kcal") is a universal unit. When food packaging says "250 calories," it means 250 kcal. The US uses "Calories" (capital C) on labels to mean kcal. In Europe and most of the world, food labels show both kcal and kJ (kilojoules). 1 kcal = 4.184 kJ.

Why is the Schofield formula used by the NHS but not US dietitians?

The UK's NHS adopted the Schofield equation for clinical nutrition guidelines because it was developed from a large international dataset that included diverse populations. The US Academy of Nutrition and Dietetics later adopted Mifflin-St Jeor after a 2005 study showed it was more accurate for the US population. Both are valid — they typically differ by less than 100 kcal for most adults.

How accurate are these calorie calculators?

BMR formulas are estimates with an error margin of about ±10–15%. Individual metabolism varies due to genetics, muscle mass, hormonal factors, gut microbiome, and other factors. The best approach is to use the calculator as a starting point, then track your weight for 2–3 weeks and adjust calories by 100–200 kcal based on actual results.

Related Calculators

More health tools

BMI Calculator BMR Calculator TDEE Calculator Body Fat Calculator Ideal Weight

Sources & Methodology

Daily calorie needs use the Mifflin–St Jeor basal metabolic rate multiplied by an activity factor. Targets reference the USDA Dietary Guidelines (US) and NHS guidance (UK).

Standards and figures reviewed 2026.