How big do Mastidoodles get?

How big is a fully grown Mastidoodle?

A fully grown Mastidoodle is one of the heaviest breeds, typically weighing between 45–90kg. This puts them in the giant dog bracket.

Male Mastidoodles 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 Mastidoodles stop growing?

Mastidoodles reach their full adult height fairly quickly, but continue to fill out in muscle and bulk after that. As a giant breed, Mastidoodles are among the slowest to mature — expect them to reach full adult size at around 18–24 months. They may look adult-sized well before that, but their bones, joints, and musculature take longer to fully develop. Avoid over-exercising giant breed puppies before they're fully grown — it can damage developing joints.

Is a Mastidoodle the right size for me?

Size matters more than people realise when choosing a dog. Here's what 45–90kg means in practice:

• Everything costs more. Food, medication, anaesthesia, and even kennels are priced by weight. Giants are expensive to own.
• Space is essential — a Mastidoodle at up to 90kg needs a home with real space and ideally a garden.
• Shorter lifespan — giant breeds typically live 8–12 years. This is simply biology — maintaining such a large body accelerates ageing.
• Physical strength — at 45–90kg, a Mastidoodle pulling on a lead is serious. Leash training from puppyhood is non-negotiable.

How do I keep my Mastidoodle at a healthy weight?

The target range for an adult Mastidoodle is 45–90kg. 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 Mastidoodles are particularly prone to weight gain. 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 Mastidoodle is a healthy weight, ask your vet at their next annual check-up. Most practices offer free nurse weight clinics.