A cat's healthy weight varies enormously by frame size, so a single target number in kilograms is much less useful than how vets actually assess it: Body Condition Score (BCS), a 1-9 scale based on what you can see and feel, not just what a scale reads.
What the Scale Actually Measures
At the healthy middle of the scale (typically 4-5 out of 9), you should be able to feel your cat's ribs easily under a thin layer of fat, see a visible waist when looking down from above, and see a slight abdominal tuck when looking from the side. Cats below this range (too thin) show ribs, spine, and hip bones that are easily visible, not just felt. Cats above this range (overweight to obese) have ribs that are difficult or impossible to feel under fat, no visible waist, and a rounded or pendulous abdomen.
Why This Matters More Than a Number on a Scale
Two cats of very different frame sizes can have completely different healthy weights in kilograms while both scoring the same, healthy BCS. Tracking BCS over time — not just weight in isolation — gives a more meaningful picture of whether your cat's body composition is actually trending toward or away from a healthy range.
Doing a Basic Check at Home
Run your hands along your cat's ribcage with light pressure — in a healthy-weight cat, you should feel the ribs without pressing hard, similar to running your fingers across the back of your hand. Look at your cat from above in good lighting — a visible waist behind the ribs is a good sign; a straight or bulging silhouette suggests excess weight. From the side, a slight upward tuck of the belly behind the ribcage is normal; a flat or sagging belly line suggests either excess weight or, in some cases, other health issues worth discussing with your vet.
When to Get a Professional Opinion
BCS assessment takes some practice, and your vet will check it at every routine visit — if you're unsure how your own at-home assessment compares, bringing it up at your next checkup is a good way to calibrate your own eye against a trained one. This is also useful context for the Growth Tracker feature on this platform, which logs weight and BCS together over time rather than weight alone.
This is educational information, not a substitute for your vet's assessment of your individual cat.