Pet Microchip Size: How Big Is a Chip?
Chips come in a spread of sizes, including mini ones for kittens and small breeds, and UK law sets the standard they all meet. What matters most is the contact record the chip's number points to.
If your puppy or kitten is booked in for their chip, it’s natural to wonder what’s actually going in. The short answer: a microchip is very small, and there’s no single fixed size.
How big is a microchip?
A pet microchip is about the size of a grain of rice: a small implant that carries a unique number a scanner can read. The grain-of-rice comparison is a good way to picture it, but it isn’t a fixed measurement. Listed glass chips run from around 1.4 mm by 8.4 mm at the smaller end up to 2.2 mm by 12.1 mm, so there’s a fair spread between the largest and smallest. Our guide to what to expect at the microchipping appointment walks through the visit itself.
Smaller chips for kittens and small breeds
Smaller “mini” chips do exist, so if you’re worried about the size of the needle for a tiny kitten or a toy breed, your vet or implanter may have options. Worth noting that the guidance on these comes from the suppliers rather than from a vet or charity body.
UK suppliers list pet chips in a range of sizes, from a 1.4 mm by 8 mm chip at the smaller end up to a 2.2 mm by 13.3 mm one described as for larger pets. “Mini” chips sit at the smaller end, around 1.4 mm by 8 mm to 1.4 mm by 9.2 mm, and are often described as suitable for cats, kittens, puppies and smaller mammals such as rabbits.
There’s no rule that small pets must get mini chips. The best next step is to ask your vet or implanter what they carry and what they suggest for your pet. Our page on where to get a puppy or kitten microchipped covers who can do it and what it tends to cost.
Types of pet microchip
In England, any chip implanted in a cat or dog must meet ISO 11784 and 11785 and respond to a scanner working at 134.2 kHz. Its unique number must also include the manufacturer’s code. A chip that meets all that is an ISO chip, and that’s what UK vets and implanters fit as standard.
Non-ISO chips exist elsewhere in the world, and if one turns up here a scanner may not be able to read it. WSAVA, the World Small Animal Veterinary Association, lists types that don’t work with every scanner, including 125 kHz chips and encrypted chips that need their own brand of reader. Some scanners are built to read ISO chips only, while others cover more frequencies.
The place this matters most is travel. GOV.UK says staff will check your pet’s microchip if it meets the ISO standards, and that if it doesn’t, you may have to bring your own reader for the journey. For a pet chipped in the UK with a compliant chip, this is unlikely to come up.
Does the type of chip matter to you?
Between one compliant chip and another, no. Every chip fitted in the UK meets the same ISO standard, so any of them does the job. What matters is the record that number points to: your name, phone number and address held on a database and linked to the chip’s number.
Once the chip is in, you can register your pet’s microchip with your own contact details, so if they’re ever found and scanned, the number leads straight back to you. If you’re still deciding when to book, our guide to the best age to microchip a puppy or kitten can help with timing.
Whichever chip your pet is given, the part that gets them home is the contact record linked to that number. Once they’re chipped, add them to Pet Database in your own name, so any scan goes straight back to you.
