How much should a healthy adult Brittany weigh?

The healthy adult weight range for the Brittany is 13.6–20.4 kg (30–45 lb). Males typically sit toward the higher end, females toward the lower end. Body condition score is a more reliable health indicator than weight alone.

My Brittany looks thin but is very muscular. Is that normal?

Yes — working Brittanys in peak condition are naturally lean, and muscle density can make them look lighter than they are. A BCS of 4 on a 9-point scale is appropriate for active field dogs. As long as ribs are palpable but not visually prominent and the dog has good energy and coat condition, lean muscularity is normal for this breed.

At what weight is a Brittany considered overweight?

A Brittany is generally considered overweight when it exceeds its ideal range (above ~20.4 kg / 45 lb for most individuals) and especially when the BCS rises above 6 on a 9-point scale — at which point ribs become difficult to feel without firm pressure and the waist tuck disappears.

Brittany Ideal Weight Guide | PetCalculator

The Brittany's ideal adult weight sits between 13.6 and 20.4 kg (30–45 lb), but athletic build and lean muscle make body condition scoring more revealing than the scale alone.