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The Formulas We Use
Every general-purpose calculator on this site is built around a specific, named equation rather than an internal estimate. Here is exactly what runs behind each one:
BMR & TDEE — Mifflin–St Jeor Equation
Basal Metabolic Rate is calculated using the Mifflin–St Jeor equation, published in 1990 and widely cited as more accurate across a broader range of body compositions than the older Harris-Benedict equation it superseded in most clinical dietetic practice:
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161
Total Daily Energy Expenditure (TDEE) is then estimated by multiplying BMR by an activity factor, a standard method used across sports-nutrition and clinical dietetics:
| Activity Level | Multiplier | Typical Description |
|---|---|---|
| Sedentary | 1.2 | Little or no exercise, desk-based work |
| 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 | Physical job or twice-daily training |
Calorie Deficit & Surplus
We use the widely cited approximation that one kilogram of body fat represents roughly 7,700 kilocalories of stored energy. Dividing the total energy gap by the number of days in your chosen timeframe gives a daily calorie adjustment. This is a simplification — real-world weight change also reflects water, glycogen, and lean-mass shifts — which is why the result is presented as an estimate alongside a safety check against commonly recommended maximum rates of change (roughly 0.5–1kg per week for fat loss).
Macronutrient Split
Protein targets are set using a grams-per-kilogram-of-bodyweight approach common in sports nutrition guidance, scaled by goal (higher for fat loss to help preserve lean mass, moderate for muscle gain, moderate for maintenance). Fat is allocated as a percentage of total calories, and the remaining calories are assigned to carbohydrate. Protein and carbohydrate are calculated at 4 kcal per gram and fat at 9 kcal per gram, the standard Atwater factors used on nutrition labels.
Body Mass Index (BMI)
BMI is calculated as weight in kilograms divided by height in metres squared, and categorised using the standard World Health Organization adult classification bands (under 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, 30+ obesity). We note on the calculator itself that BMI does not distinguish muscle mass from fat mass and is a population screening tool rather than an individual diagnostic measure.
How Restaurant Data Is Compiled
For chain and pub-menu calculators, we build a per-item dataset covering the categories a typical visitor orders from — starters, mains, sides, sauces, desserts and drinks — with values for calories, fat, saturated fat, carbohydrate, sugars, fibre, protein and salt per stated serving.
These datasets are compiled as independent estimates for general guidance, modelled on typical portion sizes and standard nutrition-composition data. They are not sourced from, licensed by, or verified against any restaurant's internal recipe data unless explicitly stated on the calculator page, and the sites they cover are not affiliated with, endorsed by, or sponsored by us. Where an operator publishes its own official nutrition information — which many larger UK chains are legally required to do under the Calorie Labelling (Out of Home Sector) (England) Regulations 2021 — we recommend cross-checking there before making decisions that matter for health, allergy or medical reasons.
Portion sizes for self-serve or build-your-own formats (such as a carvery) are inherently more variable than a fixed packaged product, since real servings depend on what staff or the customer choose to put on the plate. Our calculators handle this by letting you choose the specific items and quantities that match what you actually plan to eat, rather than offering a single average "meal" figure that could be significantly higher or lower than your real order.
Review and Update Process
Each calculator page displays a "last updated" date. We periodically review restaurant datasets against current menus and update figures when items, portions or recipes appear to have changed. General-formula calculators (BMR, TDEE, deficit, macro, BMI) are reviewed less frequently, since the underlying equations are stable and don't change with menu cycles — but we do revisit the surrounding guidance text as nutrition science and public health guidance evolves.
Known Limitations
- All formulas here are built on population averages. Individual metabolism can vary by a meaningful margin in either direction due to genetics, medical conditions, medication, and other factors a calculator cannot see.
- Restaurant nutrition figures are estimates, not laboratory-verified values for a specific dish on a specific day. Ingredient substitutions, kitchen variation, and recipe updates can all shift real values.
- None of our tools account for medical conditions such as diabetes, thyroid disorders, or eating disorders, all of which can materially change what a safe or appropriate calorie target looks like.
- Allergen information shown in restaurant calculators reflects the ingredients typically associated with an item category and is not a substitute for checking an operator's official allergen guide directly with venue staff.
Corrections Policy
If you find a figure that looks wrong, outdated, or unclear, please tell us via our Contact page. We review every report and update the relevant calculator or article where a correction is warranted. Calorie Check is built by people who would rather be told about a mistake than have it sit live.