A breed standard is the guideline which describes the ideal characteristics, temperament, and appearance of a breed and ensures that the breed is fit for function with soundness essential. Breeders and judges should at all times be mindful of features which could be detrimental in any way to the health, welfare or soundness of this breed.

Illustrating the correct method to measure a JRT

A-B Measuring height at the shoulder

C-D The Red Dots is where a terrier should be spanned by both hands for chest size, your finger's should meet underneath the chest & thumbs should meet on top or even over lap if very small chested..

E-H The silhouette of a JRT should be rectangular when measured correctly, this does not mean the dog should be long backed.


The JRT should be slightly longer that it is tall, most females are a good half inch to one inch longer than they are taller..

Credit to both JRTCGB & to the Jack Russell Terrier Club of America for the below breed standard:

Characteristics The terrier must present a lively, active and alert appearance. It should impress with its fearless and happy disposition. It should be remembered that the Jack Russell is a working terrier and should retain these instincts. Nervousness, cowardice or over-aggressiveness should be discouraged and it should always appear confident.
General Appearance A sturdy, tough terrier, very much on its toes all the time, measuring between 10" and 12" at the withers. The body length must be in proportion to the height, and it should present a compact, balanced image, always being in solid, hard condition.
Head Should be well balanced and in proportion to the body. The skull should be flat, of moderate width at the ears, narrowing to the eyes. There should be a defined stop but not overpronounced. The length of the muzzle from the nose to the stop should be slightly shorter than the distance from the stop to the occiput. The nose should be black. The jaw should be powerful and well boned with strongly muscled cheeks.
Eyes Should be almond shaped, dark in color and full of life and intelligence.
Ears Small "V" shaped drop ears carried forward close to the head and of moderate thickness.
Mouth Strong teeth with the top slightly overlapping the lower.

The left two bites are acceptable; the far left bite is preferred.
Neck Clean and muscular, of good length, gradually widening at the shoulders.
Forequarters The shoulders should be sloping and well laid back, fine at points and clearly cut at the withers. Forelegs should be strong and straight boned with joints in correct alignment. Elbows hanging perpendicular to the body and working free of the sides.
Body The chest should be shallow, narrow and the front legs not too widely apart, giving an athletic, rather than heavily chested appearance. As a guide only, the chest should be small enough to be easily spanned behind the shoulders, by average sized hands, when the terrier is in a fit, working condition. The back should be strong, straight and, in comparison to the height of the terrier, give a balanced image. The loin should be slightly arched.
Hindquarters Should be strong and muscular, well put together with good angulation and bend of stifle, giving plenty of drive and propulsion. Looking from behind, the hocks must be straight.
Feet Round, hard padded, wide, of cat-like appearance, neither turning in nor out.
Tail Should be set rather high, carried gaily and in proportion to body length, usually about four inches long, providing a good hand-hold.
Coat Smooth, without being so sparse as not to provide a certain amount of protection from the elements and undergrowth. Rough or broken coated, without being woolly.
Color White should predominate (i.e., must be more than 51% white) with tan, black, or brown markings. Brindle markings are unacceptable.
Gait Movement should be free, lively, well coordinated with straight action in front and behind.
Special Notes Old scars or injuries, the result of work or accident, should not be allowed to prejudice a terrier's chance in the show ring unless they interfere with its movement or with its utility for work or stud.

A Jack Russell Terrier should not show any strong characteristics of another breed.
Faults Shyness, Disinterest, Overly aggressive, Defects in bite, Weak jaws, Fleshy ears, Down at the shoulder, Barrel ribs, Out at elbow, Narrow hips, Straight stifles, Weak feet, Sluggish or unsound movement, Dishing, Plaiting, Toeing, Silky or woolly coats, Too much color (less than 51% white), Shrill or weak voice, Lack of muscle or skin tone, Lack of stamina or lung reserve, Evidence of foreign blood

Spanning Guid Credit to Rita Francis of Australia

Markings: What is correct & acceptable & what is not: Credit to Rita Francis of Australia