How to measure portion sizes without a scale

Portion size is where most food diaries go wrong. People are fairly good at remembering what they ate and surprisingly poor at how much — and the error is not random: we underestimate large portions and calorie-dense foods most. A kitchen scale fixes it, but nobody weighs a restaurant meal or a plate at a friend’s house. Here is how to get close without one.

Your hand is a measuring tool you always carry

Hands scale with body size, so the method roughly fits the person using it:

• Palm (thickness and size, without fingers) — a portion of meat, fish, tofu or cottage cheese, about 100–120 g, roughly 20–30 g of protein.
• Fist — a cup of cooked rice, pasta, porridge or vegetables, about 150–200 g.
• Cupped hand — a handful of nuts, dried fruit, crisps or cereal, about 30 g. With nuts that is already 170–200 kcal.
• Thumb — a tablespoon of butter, oil, peanut butter or mayonnaise, about 10–15 g, 90–130 kcal.

Studies comparing hand measures with weighed food find them about as accurate as household measures like cups and spoons — not perfect, but far better than a guess, and the errors shrink with practice.

Where the hidden calories are

1. Oil and sauces. A salad or a stir-fry can carry two or three tablespoons of oil — 300 kcal you never see. Count the fat in cooking separately when you can.
2. Drinks. Juice, sweet coffee drinks, smoothies and alcohol are easy to forget and often a few hundred calories.
3. Bites and tastes. Finishing a child’s plate, tasting while cooking, the biscuit with the tea.
4. Restaurant portions, which are usually one and a half to two home portions.

Calibrate once, then trust your eye

If you have a scale, use it for a week on the foods you eat most: your usual bowl of porridge, your glass, the amount of rice you serve yourself, your spoon of oil. You only need to learn your own plates — after that the eye remembers, and the hand method fills the gaps away from home.

Let a photo do the counting

A photo carries what words leave out: how full the plate is, how thick the slice, how much sauce. In foodoo you take a picture and the AI estimates the weight of each part of the dish, then calories and nutrients; on iPhones with LiDAR it can even measure the food’s volume in 3D. If the estimate is off, you move the portion slider — and when you keep correcting the same kind of dish the same way, foodoo learns your portions and starts the next photo from them. Our article on counting calories from a photo explains where the error comes from and how to keep it small.