Kitchen Scale or Eyeballing Portions?

You do not need a scale for every meal, and judging portions by eye is not always enough. This guide sets out what the British Nutrition Foundation (BNF) and the NHS offer as hand and spoon measures, what research says about estimating amounts, and which foods are worth weighing. It is general information for adults. For how to pick a scale, see our buying guide.

What the BNF says

The BNF's portion-size page says that if you want to measure a portion accurately, the way to do it is to weigh your food, but that this is not always easy, so it offers hand measures. It warns that portion sizes vary with the size of your hands, and says its figures are based on an average requirement of 2,000 kcal a day, so you may need more or less. Its practical measures for adults include:

• Dried pasta shapes or rice: about two handfuls, 75 g.
• Spaghetti: a bunch the size of a £1 coin, 75 g.
• Breakfast cereal: about three handfuls, 40 g.
• Baked potato: about the size of your fist, 220 g.
• Chicken breast: about the size of your whole hand, 120 g.
• Cheddar cheese: a piece about the size of two thumbs together, 30 g.
• Peanut butter: about one tablespoon, 20 g.
• Soft cheese: about three teaspoons, 30 g.

What the NHS offers

The NHS 5 A DAY page gives an adult portion of fruit or vegetables as 80 g, dried fruit as around 30 g and juice or smoothies as no more than 150 ml a day. For vegetables it uses household measures, such as three heaped tablespoons of peas or sweetcorn. For a first few weeks, a scale shows how those measures translate into grams in your own kitchen. The NHS also says weighing portions can be really helpful when you start, and that it is not something you have to do for ever.

How good is judging by eye?

A 2020 systematic review in Nutrition Reviews (Amoutzopoulos and colleagues) looked at tools used to estimate portion size in dietary research. Of 334 records reviewed, only 21 studies checked a tool against the actual amounts of food, and only a few of those were of high quality. The authors concluded that image-based tools were more accurate than food models and household utensils. That is about research tools, not your kitchen, but it fits the point that household measures are rough.

The 2025 Nature Food paper mentioned in our guide to weighing food concluded that a substantial share of the dietary reports in two large national surveys, including the UK's NDNS, had implausible energy intakes. It concerns survey records, not individuals, but it is a reminder that amounts are hard to judge without measuring.

Where a scale earns its place

A spoon or a hand is rougher for foods with a lot of energy in a small amount. McCance and Widdowson's Composition of Foods gives smooth peanut butter as 607 kcal per 100 g and olive oil as 899 kcal per 100 g. The BNF's 20 g tablespoon of peanut butter is about 121 kcal. If your heaped spoonful is 30 g, it is about 182 kcal, a gap of 61 kcal from one spoonful. Hand measures can drift in the same way for:

• Oils, spreads, nut butters and cheese. Small amounts carry a lot of energy.
• Dried pasta, rice and cereal. A handful depends on the size of the hand, and the cooked and dried weights differ a great deal.
• Foods you eat often. A small error repeated every day adds up.

Vegetables and fruit are different. The BNF says most vegetables and fruit without added sugar, salt or fat are not high in calories and should be eaten more, so a household measure is reasonable and a scale adds little. Here is a search for digital kitchen scales on Amazon (opens in a new tab) if you decide you want one.

The portion printed on a pack

A label may give values per portion as well as per 100 g. Under Regulation (EU) No 1169/2011, as it stands on legislation.gov.uk, a portion can be used only if it is quantified on the label and the number of portions in the pack is stated. The NHS warns that the manufacturer's idea of a portion may differ from yours. A scale shows the gap in seconds: weigh what you pour, compare it with the stated portion, and scale the label's figures up or down. Weighing a bowl of cereal against a printed serving is a quick way to see it.

Children's portions use the child's own hand

Hand measures are meant to scale with the person. The BNF's children's versions say cereal is about three medium handfuls, a baked potato about the size of the child's fist, cooked chicken or fish about the size of the child's hand, cooked red meat about the size of the child's palm and hard cheese about the size of two of their thumbs. The NHS gives the same idea for fruit and vegetables: as a rough guide, one portion is the amount a child can fit in the palm of their hand. Hand measures grow with the child, which is why this guide, written for adults, gives no gram weights for children.

Why portion size matters

A Cochrane review of 72 studies (Hollands and colleagues, 2015) concluded that people consistently consume more food and drink when offered larger portions, packages or tableware than smaller ones. The BNF cites it when it says that starting with smaller portions can help avoid overeating. A scale lets you decide the portion before you serve it.

A middle way

1. Weigh your usual portions of staples for a couple of weeks, such as 75 g of dried pasta or 40 g of cereal, and note how they look in your own bowl, on your own spoon and in your own hand.
2. Use measuring spoons for oils and spreads: measuring spoons on Amazon (opens in a new tab) and measuring jugs on Amazon (opens in a new tab) are searches for them.
3. Check again now and then, because portions drift over time.

Cautions

If weighing becomes rigid, step back. The NHS lists very strict habits or routines around food among the signs of an eating disorder, advises seeing a GP as soon as you can if you think you may have one, and gives the Beat helpline on 0808 801 0677. It also says pregnancy isn't the time to go on a diet. This guide is for adults: the BNF gives hand measures for children and points parents worried about a child's eating to YoungMinds and Beat.

The label on the pack is the authority on that food, and your GP or dietitian is the right person to ask about your own diet. See also our guide to scale accuracy and calibration.