🇺🇸 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.

In short

Use this for an adult BMR and TDEE estimate. Skip it if you are under 18, pregnant, or in clinical care. Average adult needs ~2,000–2,500 kcal/day (NHS/CDC population figures). TDEE = BMR × 1.2–1.9. 1 kg body fat ≈ 7,700 kcal. US dietitians prefer Mifflin-St Jeor; the NHS/WHO often use Schofield.

At a glance

Population average

2,000–2,500 kcal

Women ~2,000 · men ~2,500 (NHS/CDC)

1 kg fat

~7,700 kcal

≈ 1,100 kcal/day for 1 kg/week

US formula

Mifflin-St Jeor

Most accurate for typical adults

UK / WHO

Schofield

Clinical nutrition and children

Gender

Age

Weight (kg)

Height (cm)

Activity Level

Formula

Which calorie 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

What activity multiplier should I use?

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

How many calories should I eat to lose or gain weight?

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.

Key takeaways

Mifflin-St Jeor is the usual US adult formula. Schofield is the NHS/WHO clinical default. They usually differ by under 100 kcal.
TDEE = BMR × 1.2 (desk) to 1.9 (physical job + twice-daily training).
Safe loss is typically 0.5–1 kg/week (500–1,000 kcal/day deficit), not a crash diet.
Formulas are ±10–15%. Track two weeks, then adjust.

FAQ

Calorie questions, answered straight

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 NHS and WHO use the Schofield equation, especially for clinical nutrition and children.

What is BMR vs TDEE? ▾

BMR (Basal Metabolic Rate) is calories burned at complete rest. TDEE (Total Daily Energy Expenditure) is BMR × an activity factor. Eat at TDEE to maintain weight; eat below it to lose weight.

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

About 7,700 kcal per kilogram of body fat. That is ~1,100 kcal/day deficit. NHS and CDC recommend a maximum deficit of 500–1,000 kcal/day for 0.5–1 kg per week.

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

Yes. The NHS primarily uses Schofield (1985) for clinical nutrition. US dietetics prefers Mifflin-St Jeor. Both are typically within 5–10% for most adults, often under 100 kcal apart.

Are calories the same worldwide? ▾

Yes. Food “calories” are kilocalories (kcal). US labels use Calories (capital C) for kcal. Europe shows kcal and kJ. 1 kcal = 4.184 kJ.

How accurate are these calorie calculators? ▾

BMR formulas have about ±10–15% error. Genetics, muscle mass, hormones, and other factors vary. Start here, track weight 2–3 weeks, then adjust 100–200 kcal.

Who should skip this calorie calculator? ▾

Skip it if you are under 18 (use paediatric guidance), pregnant, or in clinical malnutrition care. This is a population estimate, not a prescribed diet.

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.