Females become sexually mature at the age of six to seven years, while males become sexually mature at about 10 years old.
The gestation period is around 15–16 months.
The calf, which typically weighs 40–60 kg (88–132 lb), is weaned after about 15 months and stays with its mother for the first two to three years of its life.
In the wild, the birth interval for this species is estimated to be four to five years; its natural offspring-rearing behavior is unstudied.

The reproductive habits of the Sumatran rhinoceros have been studied in captivity.
Sexual relationships begin with a courtship period characterized by increased vocalization, tail raising, urination, and increased physical contact, with both male and female using their snouts to bump the other in the head and genitals.
The pattern of courtship is most similar to that of the black rhinoceros.
Young Sumatran rhino males are often too aggressive with females, sometimes injuring and even killing them during the courtship.
In the wild, the female could run away from an overly aggressive male, but in their smaller captive enclosures, they cannot; this inability to escape aggressive males may partly contribute to the low success rate of captive-breeding programs.

The period of oestrus itself, when the female is receptive to the male, lasts about 24 hours, and observations have placed its recurrence between 21 and 25 days.
Rhinos in the Cincinnati Zoo have been observed copulating for 30–50 minutes, similar in length to other rhinos; observations at the Sumatran Rhinoceros Conservation Centre in Malaysia have shown a briefer copulation cycle.
As the Cincinnati Zoo has had successful pregnancies, and other rhinos also have lengthy copulatory periods, a lengthy rut may be the natural behavior.
Though researchers observed successful conceptions, all these pregnancies ended in failure for a variety of reasons until the first successful captive birth in 2001; studies of these failures at the Cincinnati Zoo discovered the Sumatran rhino's ovulation is induced by mating and it had unpredictable progesterone levels.
Breeding success was finally achieved in 2001, 2004, and 2007 by providing a pregnant rhino with supplementary progestin.

Recently, a calf was born in captivity of an endangered female in western Indonesia, only the fifth such birth in one and a quarter century.
Females become sexually mature at the age of six to seven years, while males become sexually mature at about 10 years old. The gestation period is around 15–16 months. The calf, which typically weighs 40–60 kg (88–132 lb), is weaned after about 15 months and stays with its mother for the first two to three years of its life. In the wild, the birth interval for this species is estimated to be four to five years; its natural offspring-rearing behavior is unstudied.
The reproductive habits of the Sumatran rhinoceros have been studied in captivity. Sexual relationships begin with a courtship period characterized by increased vocalization, tail raising, urination, and increased physical contact, with both male and female using their snouts to bump the other in the head and genitals. The pattern of courtship is most similar to that of the black rhinoceros. Young Sumatran rhino males are often too aggressive with females, sometimes injuring and even killing them during the courtship. In the wild, the female could run away from an overly aggressive male, but in their smaller captive enclosures, they cannot; this inability to escape aggressive males may partly contribute to the low success rate of captive-breeding programs.
The period of oestrus itself, when the female is receptive to the male, lasts about 24 hours, and observations have placed its recurrence between 21 and 25 days. Rhinos in the Cincinnati Zoo have been observed copulating for 30–50 minutes, similar in length to other rhinos; observations at the Sumatran Rhinoceros Conservation Centre in Malaysia have shown a briefer copulation cycle. As the Cincinnati Zoo has had successful pregnancies, and other rhinos also have lengthy copulatory periods, a lengthy rut may be the natural behavior. Though researchers observed successful conceptions, all these pregnancies ended in failure for a variety of reasons until the first successful captive birth in 2001; studies of these failures at the Cincinnati Zoo discovered the Sumatran rhino's ovulation is induced by mating and it had unpredictable progesterone levels. Breeding success was finally achieved in 2001, 2004, and 2007 by providing a pregnant rhino with supplementary progestin.
Recently, a calf was born in captivity of an endangered female in western Indonesia, only the fifth such birth in one and a quarter century.
Sumatran rhinoceros