Short answer
Check your puppy's collar almost every day: the Royal Kennel Club says puppy collars "should be checked almost daily for condition and fit"1. We suggest a full tape-measure re-measure of the neck and chest every two weeks while your puppy is growing fast, then monthly until the numbers stop changing.
Every day: a quick check
This article answers one question from our complete guide to sizing your puppy through the first year.
The Royal Kennel Club says: "Puppies grow rapidly and collars should be checked almost daily for condition and fit. These should not be so loose that they can slip over your puppy's head nor so tight that you cannot slip two fingers underneath."1
We suggest a quick look at the harness at the same time: front strap on the breastbone, girth strap clear of the armpits, and snug by your brand's check. Bailey & Coco says regular checks and adjustments are needed, "especially as your dog grows or if their weight fluctuates"2.
Every two weeks: re-measure
A quick check tells you whether something fits today. A tape measure tells you whether it's about to stop fitting. We suggest re-measuring every two weeks while your puppy is growing fast. This is our own suggestion, not an official figure.
| Item | What to measure |
|---|---|
| Collar | Neck, where the collar sits |
| Harness | Chest: "the widest part of your dog's chest just behind the front legs"3 |
| Crate | Length (nose to base of tail) and sitting height |
Why so often?
Because puppies change quickly. In Waggel's Golden Retriever chart, males go from 9–12 kg at 3 months to 21–26 kg at 6 months4, more than doubling. A collar or harness won't keep up with that without adjusting, and usually replacing.
Re-measure early if you notice
- You can't slip two fingers under the collar any more1.
- The collar or harness is on its loosest setting and still snug.
- Chafing or slipping. Ruffwear says that's what you may see when gear is too large or small3.
- Red marks or rubbed fur. If the skin is sore or broken, see your vet.
- Your puppy can't stand, turn around, lie down and stretch in its crate space5. Move the divider back: see how crate dividers work.
Measuring a wriggly puppy
Puppies rarely stand still. These are our own suggestions:
- Measure when your puppy is calm or sleepy, not straight after play.
- Ask a helper to hold a treat or a lick mat while you measure.
- Use a soft tape, or a piece of string you can mark and measure against a ruler afterwards.
- Measure twice and use the larger reading. Press through the coat to the body6.
- If it's not working, stop and try again later. Keep it positive, at your puppy's pace7.
When to slow down, and when to stop
When the numbers barely change over two or three measurements, we suggest moving to monthly. Keep the daily collar check1.
Don't stop at the first birthday. Breeds grow on different timetables: Canine Culture says German Shepherds are fully grown at around 18–24 months8. We suggest re-measuring monthly until the numbers stop changing, then whenever your dog's coat or weight changes. See when to re-measure and adjust your dog's harness.
Keep a simple record
We suggest writing down the date, neck and chest measurements, and the size and setting of each item. It makes it easy to see when your puppy is close to the top of a size. Measure the same way each time, with your puppy standing square.
| Date | Neck (cm) | Chest (cm) | Notes |
|---|---|---|---|
| Week 1 | Collar fitted, harness size chosen | ||
| Week 3 | |||
| Week 5 |
Breed puppy harness guides
Our puppy guides take each breed from 8 weeks to 12 months: how it grows, when to re-measure, and when to move up a size.
- Golden Retriever puppy harness size8 weeks to 12 months, stage by stage
- German Shepherd Dog puppy harness size8 weeks to 12 months, stage by stage
- Labrador Retriever puppy harness size8 weeks to 12 months, stage by stage
- English Springer Spaniel puppy harness size8 weeks to 12 months, stage by stage
Find your puppy's harness size All breeds
Questions
How often should I check my puppy's collar?
Almost daily, according to the Royal Kennel Club1.
How often should I re-measure my puppy?
We suggest every two weeks while it's growing fast, then monthly until the numbers stop changing.
When does my puppy stop growing?
It depends on the breed. Canine Culture says German Shepherds are fully grown at around 18–24 months8. Keep measuring until the numbers stop changing, and ask your vet about your puppy's growth.
Do I need to re-measure for the crate too?
Yes, if you use a divider. Your puppy should always be able to stand, turn around, lie down and stretch in the space5.