Do male and female Border Collies grow to different sizes?

Yes, males are typically a little heavier and taller than females from the same litter, though there is enough natural variation that a smaller male or a larger female is not unusual. Genetics from both parents matter more than sex alone when predicting where a specific puppy will land.

Can I tell how big my puppy will get from their paws?

Not reliably. Large paws relative to body size are a common sign that a puppy still has growing to do, but it is not a precise way to predict adult size, and by the time paws stop looking oversized most of the growing is already done anyway.

Is it a problem if my puppy is bigger or smaller than average?

Not on its own, provided they are growing steadily along their own curve rather than stalling or dropping off it. Border Collies vary more in size than many breeds because they were bred for working ability rather than a strict appearance standard, so being outside a published average is common.

How big will my Border Collie get?

Most adult Border Collies weigh somewhere between 14kg and 22kg, standing roughly 46 to 56cm at the shoulder, with males usually sitting toward the top of that range and females toward the bottom. Working-line and show-line dogs vary a little either side of this, and a puppy's paws, ears and general gangliness at four months tell you almost nothing reliable about their final size.

Reading a growth chart properly

A growth chart plots weight against age and shows a curve, not a straight line — puppies gain weight fastest in the first few months and the rate slows steadily until they reach their adult size, usually somewhere between 12 and 18 months for a medium breed like a Border Collie. What matters is whether your puppy is tracking steadily along a curve, not the exact number on any single week.

Weigh your puppy at roughly the same time of day, on the same scale, every couple of weeks, and plot it rather than comparing single readings to an average. A dog that is consistently a little above or below a published average but growing steadily is usually fine; a sudden flat week or a sharp jump is more worth noting than where the line sits overall.

Why Border Collies vary so much

Border Collies were bred purely for herding ability rather than a fixed appearance, so the breed carries more size variation than many pedigree breeds with a tighter show standard. A working-line dog from farm stock and a show-line dog bred to a breed standard can differ noticeably in build even at the same adult weight.

Sex makes a real difference too. Male Border Collies typically finish a few kilograms heavier and a couple of centimetres taller than females from the same litter, which is worth keeping in mind if you are comparing your puppy to a sibling or a parent of the opposite sex.

When growth is worth asking about

Growth plates in a dog this size typically close somewhere around 12 to 18 months, after which height is essentially fixed even if weight can still change with condition. A puppy who stops growing much earlier than that, or who is a long way off the expected curve in either direction, is worth a routine chat with your vet rather than something to work out from a chart alone.

The same goes for a puppy who plateaus suddenly after growing steadily, or who puts on weight quickly without a matching increase in height — both are more useful to flag at a normal vaccination or check-up visit than to try to diagnose from a growth chart at home.

Common questions

At what age is a Border Collie fully grown?: Most reach their adult height by around 12 months and finish filling out in weight and muscle by 18 months. Growth plates in a dog this size typically close somewhere in that window, after which height does not change even though body condition still can with age and activity level.
Do male and female Border Collies grow to different sizes?: Yes, males are typically a little heavier and taller than females from the same litter, though there is enough natural variation that a smaller male or a larger female is not unusual. Genetics from both parents matter more than sex alone when predicting where a specific puppy will land.
Can I tell how big my puppy will get from their paws?: Not reliably. Large paws relative to body size are a common sign that a puppy still has growing to do, but it is not a precise way to predict adult size, and by the time paws stop looking oversized most of the growing is already done anyway.
Is it a problem if my puppy is bigger or smaller than average?: Not on its own, provided they are growing steadily along their own curve rather than stalling or dropping off it. Border Collies vary more in size than many breeds because they were bred for working ability rather than a strict appearance standard, so being outside a published average is common.

Sources

Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.

PDSA — Pet Health Hub

Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.