Methodology
Last updated: October 14, 2026
About these numbers
Our calculators, in the articles and in the app, give you a sensible starting point. They're based on well-known formulas, but every formula is built on averages and you are not an average. Use the result, track how you get on for two or three weeks, then adjust.
Calories and maintenance
We estimate the energy your body burns at rest with the Mifflin-St Jeor equation, which research has found to be one of the more accurate options for most adults: Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 We then multiply that by how active you are: 1.2 if you mostly sit, 1.375 for light activity, 1.55 for moderate, 1.725 for very active and 1.9 for athletes or physical jobs. We round to the nearest 10 calories. The muscle-gain calculator adds whatever surplus you pick on top.
Protein
Protein targets are shown as a range per kg of body weight: 1.2 to 1.6 g to maintain, 1.6 to 2.2 g to build muscle and 1.8 to 2.4 g while dieting, to help hold on to muscle. These come from sports nutrition research on adults who exercise. If you have kidney disease, please get your number from your doctor instead.
BMI
BMI is your weight in kg divided by your height in metres squared, sorted into the standard adult WHO groups. It's a quick screening number and nothing more. It can't tell muscle from fat and isn't meant for children or during pregnancy.
Body fat
Our body fat estimate uses the US Navy tape-measure method (height, neck and waist, plus hips for women) and groups the result using American Council on Exercise ranges. It can be a few percentage points off compared with a lab scan. Its real value is tracking change over time, so measure the same way each time.
Meal photos and food search in the app
When you snap a photo or type what you ate, AI identifies the food and estimates the portion and nutrition. We check results for impossible values before saving them, but a photo can't see the oil in the pan or exactly how big a portion is. You can always edit a result before logging it. Barcode results use product data, which can occasionally differ from the label in your hand.
When to check with a doctor
If you have a medical condition, take medication that affects appetite or blood sugar, or are pregnant, please check any targets with your doctor before using them.
Get in touch
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