A measuring cup is a guess with a handle. Fill the same cup 10 times with the same dry food and you will be off by 20–40% between the lightest and heaviest scoop — on a 50 g portion that is 10–20 g, or 35–70 kcal. A 1 g kitchen scale removes that error for about 20 USD, and combined with a weekly weight and a body condition score, it turns feeding from an opinion into 2 numbers you can act on.
Why the cup is off by 20–40%
Dry food is not a liquid. Kibble size, how full the scoop is, whether the food settled in the bag, and how level the top is all change the mass in the same volume. A level 240 ml cup of a 4 mm kibble holds roughly 90 g; the same cup heaped holds 120–130 g, and a cup of a small 8 mm ring-shaped kibble holds 70 g. Three people scooping from the same bag with the same cup commonly land 20–40% apart. That is the difference between a 4.5 kg cat holding steady and gaining 400 g in 6 months.
Setting up a 1 g scale
Any kitchen scale that reads to 1 g and holds 2 kg is enough and costs 15–25 USD; 0.1 g scales cost more and only matter for kittens under 8 weeks. Yearly food and vet spend is laid out on the cost breakdown page. Put the bowl on the scale, press tare, add food until the number is right, and never scoop straight from the bag into the bowl — the bag rim alone can add 5–15 g of crumbs. Weigh the day's total once and split it into 2 or 3 meals by eye, or weigh each meal if the cat is on a weight-loss plan. Check the scale monthly with a 100 g reference: a 200 g test weight should read 199–201 g, and a 3 g drift is enough to add 10% to a small cat's intake over 30 days.
Grams are not calories
Two foods at 4.0 and 4.6 kcal per gram differ by 15% per gram, so a portion that was correct on the old bag is 15% too much on the new one. Most dry maintenance foods sit at 3.5–4.5 kcal/g; most canned foods at 0.9–1.3 kcal/g, which is why 80 g of wet food is not 80 g of dry. A 4.5 kg indoor adult cat usually needs 180–240 kcal a day, and a 5 kg cat on a weight-loss plan 140–170 kcal. Convert once: grams per day equals target kcal divided by kcal per gram. Write that number on the lid.
The weekly weigh, done the same way every time
Weigh on the same scale, same time of day, before the first meal, once every 7 days. A 5 g resolution baby scale for adults, a 1 g kitchen scale with a 2 kg tray for kittens. Three readings in a row are a trend; one reading is noise, because a full bladder is worth 50–100 g. Log grams, not adjectives. In a 4-cat home, weigh each cat in the same order and keep 1 line per cat per week, so a 3-week drift shows up before the ribs do.
Body condition score: the second track
Weight alone misses the cat that is losing muscle and gaining fat. Use the 9-point body condition score (BCS) once a month: ribs felt with light pressure at 5, seen at 7, not felt at 9; a waist visible from above at 5, absent at 7; a 2 cm abdominal fat pad at 5, a 4 cm pad at 8. Ideal is 4–5 of 9. At 8 or 9 of 9, start a weight plan at 80% of current intake. At 1–3 of 9, stop any diet and book a vet visit — muscle loss in an older cat is a disease signal, not a feeding problem.
Losing 1–2% of body weight per week
Safe loss is 1–2% of body weight per week, which for a 6 kg cat is 60–120 g a week, or 240–480 g a month. Faster than 2% a week risks losing muscle and, in a cat that stops eating for 2–3 days, hepatic lipidosis. Slower than 1% a week usually means the portion is 10–20% too high or the cat is eating the dog's food. Recalculate the target every 4 weeks, because a 5.4 kg cat needs fewer calories than a 6.0 kg cat — keep feeding the old amount and loss stalls at 0.3% a week.
Measuring method versus real error
| Method | Typical error | Grams off on a 50 g portion | kcal off at 4 kcal/g |
|---|---|---|---|
| Eyeballed half cup | 30–50% | 15–25 g | 60–100 kcal |
| Same cup, level fill | 20–40% | 10–20 g | 40–80 kcal |
| Same cup, heaped fill | 35–45% | 18–23 g | 72–92 kcal |
| 1 g kitchen scale | 1–2% | 0.5–1 g | 2–4 kcal |
| 0.1 g scale, tared bowl | 0.5% | 0.2–0.5 g | 1–2 kcal |
Wet food, mixed feeding and treats
Weigh the can too. A 85 g can is 85 g only if you scrape it; 5–10 g left on the sides is 7–12% of the meal. Treats count: 10 kcal of treats is 5% of a 200 kcal day, and 5 treats at 2 kcal each is 10 kcal, which is 30 g of body weight a month if unaccounted. Cap treats at 10% of daily kcal, and subtract them from the weighed meal rather than adding them on top. If you feed wet and dry, weigh both and add the kcal — the calorie density explainer has the per-gram math, and carb content matters if the cat is diabetic.
When the scale will not move
Book a vet visit if weight drops 5% in 3 months, if a cat on 80% of calculated intake loses nothing in 4 weeks, or if BCS falls to 3 of 9 or below. Ask for a thyroid panel in cats over 8 years, a glucose check, and a fecal. Also check the boring things first: a second feeder in the house, a neighbour feeding the cat, a 15% label change on a reformulated food, and a scale that has drifted 3 g. A diet that fails on paper usually fails on measurement, not on metabolism.
Start tonight with 5 steps:
- Weigh 10 level cups of your current food and average them.
- Buy a 1 g kitchen scale and tare the bowl at every meal.
- Convert the bag's kcal per gram into grams per day, write it on the lid.
- Weigh the cat weekly, same time, and score BCS monthly.
- Target 1–2% loss per week and recalculate every 4 weeks.
Terms mentioned in this article
Frequently asked
Is a 1 g kitchen scale accurate enough for cat food?
Yes for any cat over 8 weeks. A 1 g scale keeps error at 1 to 2% on a 50 g portion, against 20 to 40% for a measuring cup. Check it monthly with a 100 g reference weight, because a 3 g drift adds about 10% to a small cat's daily intake over a month.
How fast can my cat safely lose weight?
Aim for 1 to 2% of body weight per week, which is 60 to 120 g a week for a 6 kg cat. Faster loss burns muscle, and a cat that stops eating for 2 to 3 days risks hepatic lipidosis. Recalculate the calorie target every 4 weeks, since a lighter cat needs less food.
My cat's weight is stable but it looks fatter. Which number do I trust?
Trust the body condition score. A 9-point score catches muscle loss masked by fat gain, which weight alone hides. Score monthly: ribs felt with light pressure is 5 of 9, ribs visible is 7, ribs not felt is 9. Ideal is 4 to 5, and 8 or 9 means starting a weighed weight-loss plan.