Javan rhinos are smaller than the Indian rhinoceros, and are close in size to the black rhinoceros. They are the largest animal in Java and the second-largest animal in Indonesia after the Asian elephant. The length of Javan rhinos including their head is 2 to 4 m (6.6 to 13.1 ft), and they can reach a height of 1.4–1.7 m (4.6–5.6 ft). Adults are variously reported to weigh between 900 and 2,300 kg (2,000 and 5,100 lb), although a study to collect accurate measurements of the animals has never been conducted and is not a priority because of their extreme conservation status. No substantial size difference is seen between genders, but cows may be slightly bigger. The rhinos in Vietnam appeared to be significantly smaller than those in Java, based on studies of photographic evidence and measurements of their footprints.
Like the Indian rhino, the Javan rhinos have a single horn (the other extant species have two horns). Its horn is the smallest of all extant rhinos, usually less than 20 cm (7.9 in) with the longest recorded only 27 cm (11 in). Only bulls have horns. Cows are the only extant rhinos that remain hornless into adulthood, though they may develop a tiny bump of an inch or two in height. Javan rhinos do not appear to often use their horn for fighting but instead uses it to scrape mud away in wallows, to pull down plants for eating, and to open paths through thick vegetation. Similar to the other browsing species of rhino (black and Sumatran), Javan rhinos have a long, pointed, upper lip which helps in grabbing food. Their lower incisors are long and sharp; when Javan rhinos fight, they use these teeth. Behind the incisors, two rows of six low-crowned molars are used for chewing coarse plants. Like all rhinos, Javan rhinos smell and hear well, but have very poor vision. They are estimated to live for 30 to 45 years.
Their hairless, splotchy gray or gray-brown skin falls in folds to the shoulder, back and rump. The skin has a natural mosaic pattern, which lends the rhino an armored appearance. The neck folds of Javan rhinos are smaller than those of the Indian rhinoceros, but still, form a saddle shape over the shoulder. Because of the risks of interfering with such an endangered species, however, Javan rhinos are primarily studied through fecal sampling and Camera traps. They are rarely encountered, observed or measured directly
