A martingale collar should be sized so it slips comfortably over your greyhound's head when open, then closes to sit snugly — but never tightly — around the neck. Because a sighthound's head is narrower than its neck, getting these two measurements right is the whole job. This guide shows you exactly how to measure, which width to choose, and the mistakes that lead to a collar that either slips off or sits too tight.
Why greyhounds need a martingale collar, not a flat one
Greyhounds, whippets and other sighthounds have heads that are narrower than their necks, so an ordinary flat collar can slide straight off — especially if the dog backs up or spooks. A martingale is a limited-slip collar: when the dog pulls, the control loop gently closes the collar just enough that it can't pass back over the ears, then releases as soon as tension stops. Unlike a slip lead or choke chain, a correctly sized martingale never constricts the throat. That combination of security and gentleness is why it's the standard collar for sighthounds.
What you need to measure
You need two measurements, taken with a soft fabric tape measure (a piece of string and a ruler also works):
- Head width — the circumference of the widest point of the head, just behind the ears. This is the opening the collar has to pass over.
- Neck circumference — measured around the mid-neck, where the collar will actually sit.
Measure on a calm, standing dog, snug against the coat but without compressing it, and write both numbers down in centimetres.
How to measure your greyhound, step by step
- Stand your dog squarely and keep them relaxed.
- Wrap the tape around the head at its widest point, just behind the ears, and note the measurement.
- Wrap the tape around the neck where the collar will rest, and note that measurement.
- Keep both numbers handy when you choose a size on the product page.
How to choose the right size
A martingale works between two limits. When open, it has to clear the head measurement so it can go on and off. When the control loop is pulled tight, it should close down to roughly the neck measurement — snug enough that it can't slip back over the ears. Pick the size whose range covers your neck measurement while the relaxed collar still passes over the head.
Use the two-finger rule: with the martingale fully tightened, you should still be able to slide two fingers between the collar and the neck. If you can't, size up; if it slips over the ears when closed, size down. Match your measurements to the size options shown on each product page.
Which width: 40 mm, 25 mm or 20 mm?
Width is about comfort and pressure distribution, not just looks. As a rule:
| Width | Best for |
|---|---|
| 40 mm | Full-size greyhounds, lurchers and larger crosses — the extra width spreads pressure across the neck. |
| 25 mm | Whippets, smaller greyhounds and slimmer necks — a lighter everyday option. |
| 20 mm (biothane) | Italian greyhounds, puppies and lightweight dogs — minimal weight, waterproof and easy to clean. |
A wider collar distributes pressure more gently and makes a stronger visual statement; a narrower one is lighter on a delicate neck.
Browse the 40 mm martingale collars, the 25 mm collars, or the 20 mm biothane collars.
How tight should a martingale collar sit?
At rest, a martingale should hang comfortably loose. When the dog pulls, the control loop closes the collar just enough that it can't pass back over the ears — and no further. Fully tightened, it should still leave room for two fingers between collar and neck. If it constricts the throat, it's acting like a choke collar, which is exactly what a martingale is designed to avoid.
Common sizing mistakes to avoid
- Ordering by breed name instead of measuring. Two greyhounds can need different sizes; always go by your own numbers.
- Sizing only the neck. The collar also has to clear the head — check both measurements.
- Too loose. A collar that doesn't close below the head measurement can slip off, defeating the point of a martingale.
- Too tight when closed. If the two-finger check fails, the collar is too small.
- Forgetting to re-measure puppies. Young dogs grow quickly — re-check the fit regularly.
Frequently asked questions
How do I measure my greyhound for a martingale collar?
Measure two points with a soft tape: the widest part of the head behind the ears, which the collar must slide over, and the neck where the collar will sit. Choose a size that fits over the head when open and closes snugly to the neck measurement.
What width martingale collar is best for a greyhound?
40 mm suits full-size greyhounds and lurchers because it spreads pressure across the neck. 25 mm suits whippets and slimmer necks, and 20/40 mm biothane suits Italian greyhounds and lighter dogs.
How tight should a martingale collar be?
When fully tightened it should still allow two fingers between the collar and the neck. It should stop the collar slipping over the ears, not constrict the throat.
Can a dog slip out of a martingale collar?
Properly sized, no — preventing escape is its purpose. If a dog slips out, the collar is too large: the closed control loop should be smaller than the head measurement.
Are martingale collars safe for everyday wear?
Yes, for walks and supervised wear. As with any limited-slip collar, remove it during crating or unsupervised time to avoid snagging.