Mastiff Weight Chart by Age

An adult male Mastiff weighs 160.0–230.0 lb (72.6–104.3 kg) and an adult female 120.0–170.0 lb (54.4–77.1 kg), according to the American Kennel Club breed standard.

At 3 months a typical male weighs 40.1 lb (18.2 kg) and a typical female 33.9 lb (15.4 kg). Half of males weigh 24.5–59.3 lb (11.1–26.9 kg), and half of females 22.9–47.1 lb (10.4–21.4 kg). A typical puppy is around 26% of its adult weight at this age.

At 4 months a typical male weighs 61.3 lb (27.8 kg) and a typical female 50.9 lb (23.1 kg). Half of males weigh 38.9–88.6 lb (17.6–40.2 kg), and half of females 35.5–69.0 lb (16.1–31.3 kg). A typical puppy is about 40% of the way to adult weight.

At 6 months a typical male weighs 98.9 lb (44.8 kg) and a typical female 79.5 lb (36.1 kg). Half of males weigh 63.8–140.8 lb (29.0–63.8 kg), and half of females 56.8–106.4 lb (25.8–48.3 kg).

At 12 months a typical male weighs 142.6 lb (64.7 kg) and a typical female 112.5 lb (51.0 kg). Half of males weigh 92.6–198.9 lb (42.0–90.2 kg), and half of females 81.5–148.6 lb (37.0–67.4 kg). That is about 92% of final weight, with the rest filling in over the following months.

Dogs of this size that were weighed both as puppies and as adults ended up at about 2.5 times their 4-month weight, in records from US veterinary clinics. The calculator on the home page uses those records for the puppy’s own age and weight, and returns a range rather than one number.

Height is usually settled first; weight keeps filling in for longer. On the growth curve for its size, a Mastiff stays above 95% of adult weight from about 14 months, and the last 8% after its first birthday comes on slowly.

Yes, and by enough to matter. Adult males run 160.0–230.0 lb (72.6–104.3 kg) against 120.0–170.0 lb (54.4–77.1 kg) for females. Comparing a female against a chart that does not separate the sexes will usually make her look underweight when she is not.

A giant breed, defined by adult weight. That classification determines the growth curve used here: veterinary research shows dogs of similar adult size grow at similar rates regardless of breed.

Not necessarily: 1 in 10 healthy puppies weighs less than the lightest figure in the table. What matters more is the trend. A puppy that drifts from one part of the range to a lower one is worth checking: look at its body condition and ask your vet about its diet. A single low reading is not a diagnosis.

Body condition tells you more than the scale. You should be able to feel the ribs under a thin layer of fat without pressing, see a waist from above, and see the belly tuck up from the side. A dog can sit inside the weight range and still carry too much fat.

Most published charts come from one breeder’s litters or from unsourced rules of thumb, and many do not say whether the figures are for males, females or both. The ranges here come from centile curves fitted to millions of veterinary bodyweight records, scaled to the AKC adult range, and split by sex.

The research behind these curves found neutering shifted growth trajectory only slightly, by less than the variation between individual dogs, so separate curves were not needed. Neutering is associated with a higher chance of becoming overweight in adulthood, which is a body condition question rather than a growth chart one.

An adult Mastiff weighs 72.6–104.3 kg for males and 54.4–77.1 kg for females under the American Kennel Club standard. A typical male weighs 18.2 kg at 3 months, 44.8 kg at 6 months and 64.7 kg at 12 months; a typical female 15.4 kg, 36.1 kg and 51.0 kg. The charts above give every month in kilograms, with a switch to pounds.

The American Kennel Club standard gives females 120.0–170.0 lb (54.4–77.1 kg). A typical female Mastiff weighs 50.9 lb at 4 months, 79.5 lb at 6 months and 112.5 lb at 12 months. Weight stays above 95% of the adult figure from about 14 months. The female chart above gives every month.

The American Kennel Club standard gives males 160.0–230.0 lb (72.6–104.3 kg). A typical male Mastiff weighs 61.3 lb at 4 months, 98.9 lb at 6 months and 142.6 lb at 12 months. Weight stays above 95% of the adult figure from about 14 months. The male chart above gives every month.