Mastiff Growth Chart: Puppy Weight by Month

Mastiff puppy weight chart (lb)

Adult weight	2 mo	3 mo	4 mo	5 mo	6 mo	8 mo	10 mo	12 mo	15 mo	18 mo
Male, 160 lb	21	36	53	69	83	106	125	138	150	157
Male, 230 lb	31	52	77	100	120	153	180	198	216	225
Female, 120 lb	16	27	40	52	62	80	94	103	113	118
Female, 170 lb	23	38	57	74	88	113	133	146	160	167

Mastiff puppy weight chart (kg)

Adult weight	2 mo	3 mo	4 mo	5 mo	6 mo	8 mo	10 mo	12 mo	15 mo	18 mo
Male, 73 kg	9.7	16	24	31	38	48	57	62	68	71
Male, 104 kg	14	23	35	45	54	69	82	90	98	102
Female, 54 kg	7.3	12	18	24	28	36	43	47	51	53
Female, 77 kg	10	17	26	33	40	51	60	66	72	76

Typical weights by month. Individual puppies often sit 10–15% above or below these numbers. Last reviewed October 7, 2026.

How big does a Mastiff get?

According to the American Kennel Club's breed profile for the Mastiff, adults weigh: male 160–230 lb; female 120–170 lb. Life expectancy is 6–10 years.

	Weight	Height
Male	160–230 lb	30 in & up
Female	120–170 lb	27.5 in & up

When does a Mastiff stop growing?

Mastiffs grow like other giant-sized dogs: they are close to adult weight at around 18 months. At 6 months a typical Mastiff puppy has reached about 52% of its adult weight.

To estimate your own puppy's adult weight from its current weight and age, use the puppy weight calculator and choose "Giant" as the expected adult size.

How the chart is made

The adult weights come from the AKC breed profile. The weight at each month is estimated with our giant-breed growth curve, which gives the share of adult weight a typical puppy of that size reaches at each age. The curves are simplified from published research on dog growth, including the growth standard charts by Salt and colleagues (PLOS ONE, 2017).

If your puppy is well below or above the chart, stops gaining weight, or looks very thin or round, ask your vet to check its body condition.

Questions people ask

How much should a 3-month-old Mastiff weigh?

Typically about 27–52 lb, depending on sex and how big the dog will be as an adult.

How much should a 6-month-old Mastiff weigh?

Typically about 62–120 lb, roughly 52% of adult weight.

When is a Mastiff full grown?

Most Mastiffs are close to their adult weight at around 18 months, though many keep filling out with muscle for a while after that.

How big will my Mastiff get?

The AKC lists adult weights of male 160–230 lb; female 120–170 lb. Your puppy's parents are a good guide to where in that range it will end up.

Mastiff growth chart