How big do Sussex Spaniels get?

How big is a fully grown Sussex Spaniel?

A fully grown Sussex Spaniel is a mid-sized dog, typically weighing between 16–20kg. This puts them in the medium dog bracket.

Male Sussex Spaniels tend to be larger than females, generally weighing toward the upper end of that range. Females are typically lighter and slightly shorter. Individual variation within the breed is normal — genetics, diet, and health all play a role.

When do Sussex Spaniels stop growing?

Sussex Spaniels reach their full adult height fairly quickly, but continue to fill out in muscle and bulk after that. Medium breeds like the Sussex Spaniel tend to be fully grown by 10–12 months, earlier than larger dogs. They fill out quickly and most look fully adult by their first birthday, though some development continues into their second year.

Is a Sussex Spaniel the right size for me?

Size matters more than people realise when choosing a dog. Here's what 16–20kg means in practice:

• Food costs increase with size — a Sussex Spaniel at 20kg needs significantly more food than a small breed.
• Space requirements — a medium breed needs room to move. A small flat works if exercise needs are met, but they do better with outdoor space.
• Pet insurance is higher. Larger breeds cost more to insure because treatments and surgeries scale with body weight.
• Lifespan is affected — medium breeds live 11–13 years on average.

How do I keep my Sussex Spaniel at a healthy weight?

The target range for an adult Sussex Spaniel is 16–20kg. A simple check: you should be able to feel their ribs without pressing hard, but you shouldn't be able to see them. Viewed from above, there should be a visible waist.

Obesity is the most preventable health problem across all dog breeds — and Sussex Spaniels are not immune to it. Measure food portions rather than estimating, limit treats to 10% of daily calories, and factor in daily exercise as part of their routine.

If you're unsure whether your Sussex Spaniel is a healthy weight, ask your vet at their next annual check-up. Most practices offer free nurse weight clinics.