Norway lemmings weigh between 20 and 130 g. Body length ranges from 8 to 17.5 cm. They have thick bodies with heavy coats for maintaining body heat against the cold. Fur colour is black and brown with some golden-yellow streaks. The underbelly is a lighter colour than the rest of their fur. Norway lemmings retain the same fur colour, regardless of season, and the males and females are generally similar in size and colour. They do not have a conspicuous tail. Their teeth are characteristic of their subfamily, Microtinae: 12 molars, 4 incisors and flattened crowns. Their limbs are short and mostly tucked under the body. The claw of the first digit on each paw is larger and flatter than the rest of the claws. This modification helps lemmings to tunnel through snow. Their basal metabolic rate is 1.0710 W.