Garter Snake Size Comparison: Just How Big Do They Get?

Written by Rob Amend
Published: July 2, 2023
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About 150 species of snakes live in the United States. The majority of these are non-venomous and mostly harmless. They play a vital role in controlling the population of rodents and other pests. Garter snakes (genus Thamnophis) are common in the United States and are our frequent companions while gardening or working outside. Garter snakes vary considerably, so how do they compare to other snakes, and how big do they get?

A Few Facts About Garter Snakes

  • Most snakes lay eggs, but the common garter snake will give birth to 10-40 live snakes, which are immediately independent.
  • Garter snakes are flexible and can twist into more defensive positions than other snakes.
  • When they mate, garter snakes form into groups, or “mating balls,” made of more than a dozen males and one or more females.
  • Though some snakes seem frightening, garter snakes are essential to pest control for gardens and urban areas.
  • Garter snakes are relatively harmless, though their bites contain some venom to help subdue their prey. This venom is not strong enough to harm humans.
A profile shot of an Eastern Garter Snake (Thamnophis sirtalis sirtalis). Shot in Waterloo, Ontario, Canada.

The average garter snake is about the same size as the width of a yoga mat.

©Chris Hill/

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Types of Garter Snake

Garter snakes are distributed widely throughout North America, with about 35 species listed in the chart below.

Common NameScientific NameDistribution
Aquatic garter snakeThamnophis atratusArizona and New Mexico, and in the Mexican states of Sonora, Chihuahua, and Durango
Blackbelly garter snakeThamnophis melanogasterMexico
Blackneck garter snakeThamnophis cyrtopsisCentral California
Bogert’s garter snakeThamnophis bogertiOaxaca, Mexico
Butler’s garter snakeThamnophis butleriSouthwestern United States, Mexico, and Guatemala
Checkered garter snakeThamnophis marcianusSouthwestern United States, Mexico, and Central America
Common garter snakeThamnophis sirtalisNorth America
Conant’s garter snakeThamnophis conantiPuebla and Veracruz, Mexico
Cope’s mountain meadow snakeThamnophis copeiMexico
Fox’s mountain meadow snakeThamnophis foxiMexico
Giant garter snakeThamnophis gigasArizona and New Mexico, and in the Mexican states of Sonora, Chihuahua, and Durango
Godman’s garter snakeThamnophis godmaniCentral California
Goldenhead garter snakeThamnophis chrysocephalusMexico
Highland garter snakeThamnophis fulvusMexico, Guatemala, Honduras and El Salvador
Liner’s garter snakeThamnophis lineriMexico
Longtail alpine garter snakeThamnophis scalarisMexico
Madrean narrow-headed garter snakeThamnophis unilabialisMexico
Mexican garter snakeThamnophis equesMexico and in the United States (Arizona and New Mexico)
Mexican wandering garter snakeThamnophis erransChihuahua, Durango, Jalisco, Nayarit, and Zacatecas States of Mexico
Montane garter snakeThamnophis exsulMexico
Narrow-headed garter snakeThamnophis rufipunctatusCentral California to Baja California, Mexico
Northwestern garter snakeThamnophis ordinoidesCalifornia, Oregon, and Washington; in Canada, it is found in British Columbia
Plains garter snakeThamnophis radixSouthern Mexico
Ribbon snakeThamnophis sauritaEastern North America
Rossman’s garter snakeThamnophis rossmaniMexico
Short-tail alpine garter snakeThamnophis scaligerMexico
Shorthead garter snakeThamnophis brachystomaCentral United States as far north as Canada and as far south as Texas
Sierra garter snakeThamnophis couchiiCalifornia and Oregon in the United States
Southern Durango spotted garter snakeThamnophis nigronuchalisDurango, Mexico
Sumichrast’s garter snakeThamnophis sumichrastiMexico
Tamaulipan montane garter snakeThamnophis mendaxMexico
Tepalcatepec Valley garter snakeThamnophis postremusMexico
Two-striped garter snakeThamnophis hammondiiCentral British Columbia, central Alberta, and southwestern Manitoba in Canada, Central United States
West Coast garter snakeThamnophis validusMexico
Western ribbon snakeThamnophis proximusCentral California to Baja California, Mexico
Western terrestrial garter snakeThamnophis eleganscentral British Columbia, central Alberta, and southwestern Manitoba in Canada, Central United States
Yellow-throated garter snakeThamnophis pulchrilatusMexico

Garter Snake Size: How Big Do They Get?

Snakes vary tremendously in size, from the green anaconda growing up to 30 feet in length to the Barbados threadsnake, measuring up to about 4.09 inches. Garter snakes run toward the smaller side, reaching 18 to 51 inches—somewhere between the length of a windshield wiper and one-and-a-half golf putters.

Growing as long as one-and-a-half golf putters, garter snakes are not the longest.

©Matt Jeppson/

Garter Snake Size: Largest Garter Snake Ever Recorded

Though they range from 18 to 51 inches, most garter snakes will be between 22 and 30 inches. Occasionally, though, a garter snake will exceed this size.

In 2006, Jonathan Wiens, a master’s student at the University of Manitoba, discovered a red-sided garter snake with a length of 52.8 inches—the largest garter snake on record. He found the female while monitoring a den of snakes near Manitoba. The snake was over 12 years old, much older than the usually expected 4 to 5 years.

Places You’re Most Likely to Encounter a Garter Snake

Where you are most likely to encounter a garter snake has a little bit to do with distribution and a bit to do with the environment you find yourself in.

Garter Snake Range

As the most widely distributed snake in North America, garter snakes are present in all of the contiguous United States. The map below shows how many species are in each state.

Garter snakes live in all of the contiguous United States.

Garter Snake Habitations

Much of the diet of garter snakes depends on the presence of amphibians. This explains their need to be close to water. Many of the species in the western parts of North America are more aquatic than otherwise. They can adapt to many habitats as long as water is nearby. Garter snakes live in forests, fields, grasslands, woodlands, and suburban lawns. You can sometimes see them near ponds with tall, grassy weeds. These are the places you are most likely to encounter a garter snake.

Texas Garter Snake

Garter snakes are large enough to hunt pests and small enough to get away quickly from threats.

©Cathleen Wake Gorbatenko/


Garter snakes live throughout North America and provide excellent pest control. Their bites are relatively harmless to humans, and they try to flee rather than attack when threatened. Their size also contributes to their non-threatening appearance, with lengths ranging from 18 to 51 inches.

The photo featured at the top of this post is © Eric Dale/

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About the Author

Rob Amend is a writer at A-Z Animals, primarily covering meteorology, geology, geography, and animal oddities. He attained a Master's Degree in Library Science in 2000 and served as reference librarian in an urban public library for 22 years. Rob lives in Cincinnati, Ohio, and enjoys spending time with his family, hiking, photography, woodworking, listening to classic rock, and watching classic films—his favorite animal is a six-foot-tall rabbit named Harvey.

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