Neck
Using a tape measure or a length of string (measure with a ruler), measure right around your dog's neck where a collar would typically sit. A comfortable fit will allow two fingers (flat) to be placed between the collar and your dog's neck.

Chest
Using a tape measure or a length of string (measure with a ruler), measure right around your dog, starting at its shoulder blades, down to the deepest point of its chest, and back up again. This measurement is usually taken from just behind your dog's front legs.

Back
Using a tape measure or a length of string (measure with a ruler), measure from your dog's shoulder blades down to the base of its tail.

Collars

Extra-Small
Neck:  19 - 26cm | 7½ - 10¼"
Width:  1.5cm | ⅝"
Size:  Chihuahua, Brussel Griffon, Small Terrier

Small
Neck:  25 - 33cm | 9¾ - 13"
Width:  1.5cm | ⅝"
Size:  Italian Greyhound, Mini Dachshund, Jack Russell

Medium
Neck:  32 - 43cm | 12½ - 17"
Width:  2cm | ¾"
Size:  French Bulldog, Mini Schnauzer, Pug, Cavalier

Large
Neck:  42 - 54cm | 16½ - 21¼"
Width:  2.5cm | 1"
Size:  Weimaraner, Labrador, Husky

Leads

One Size
Length:  120cm | 47"
Width:  2.2cm | ⅞" 
Size:  All breeds

Harnesses

Small
Neck:  31cm | 12¼"  (fits up to) 
Chest:  37 - 52cm | 14½ - 20½"
Size:  Mini Dachshund, Jack Russell, Maltese, Pomeranian

Medium
Neck:  38cm | 15"  (fits up to)
Chest:  45 - 65cm | 17¾ - 25½"
Size:  French Bulldog, Mini Schnauzer, Whippet, Cavalier

Large
Neck:  45cm | 17¾"  (fits up to)
Chest:  55 - 78cm | 21¾ - 30¾"
Size:  French Bulldog, Pug, Dachshund, Cocker Spaniel

Hoodies

Extra-Small
Neck:  26cm | 10"  (fits up to)   
Chest:  33cm | 13"  (fits up to) 
Back:  26cm | 10"
Size:  Chihuahua, Brussel Griffon, Small Terrier

Small
Neck:  33cm | 13"  (fits up to) 
Chest:  48cm | 19"  (fits up to)
Back:  26cm | 10"
Size:  Italian Greyhound, Mini Dachshund, Jack Russell

Medium
Neck:  46cm | 18"  (fits up to)
Chest:  55cm | 21½"  (fits up to)
Back:  35cm | 13½"
Size:  French Bulldog, Mini Schnauzer, Pug, Cavalier

Large
Neck:  47cm | 18½"  (fits up to)
Chest:  65cm | 25½"  (fits up to)
Back:  40cm | 16"
Size:  French Bulldog, Pug, Dachshund, Cocker Spaniel

Extra-Large
Neck:  53cm | 21"  (fits up to)
Chest:  72cm | 28½"  (fits up to)
Back:  44cm | 17"
Size:  Labrador, Husky

Turtlenecks

Extra-Small
Neck:  26cm | 10"  (fits up to)   
Chest:  30cm | 11½"  (fits up to) 
Back:  26cm | 10"
Size:  Chihuahua, Brussel Griffon, Small Terrier

Small
Neck:  30cm | 11½"  (fits up to) 
Chest:  33cm | 13"  (fits up to)
Back:  33cm | 13"
Size:  Italian Greyhound, Mini Dachshund, Jack Russell

Medium
Neck:  37cm | 14½"  (fits up to)
Chest:  39cm | 15½"  (fits up to)
Back:  38cm | 15"
Size:  French Bulldog, Mini Schnauzer, Pug, Cavalier

Large
Neck:  42cm | 16½"  (fits up to)
Chest:  45cm | 17½"  (fits up to)
Back:  44cm | 17"
Size:  French Bulldog, Pug, Dachshund, Cocker Spaniel

Extra-Large
Neck:  53cm | 21"  (fits up to)
Chest:  53cm | 21"  (fits up to)
Back:  50cm | 19½"
Size:  Labrador, Husky