In ancient time, 1 tan was equivalent to 9 sun (unit of length) and 5 bu (分; unit of length; approximately 28.785 centimeters) to 1 shaku (approximately 30.3 centimeters) in width and 2 jo and 8 shaku (approximately 8.48 meters) to 3 jo (approximately 9.09 meters) in length for silk clothes, and 9 sun and 5 bu (approximately 28.785 centimeters) in width and 2 jo and 8 shaku (approximately 8.48 meters) in length for menpu (cotton cloth; cotton material) (measured using kujira-jaku [unit of length, 1 kujira-jaku is approximately 37.9 centimeters]).
古代には、絹布では幅9寸5分～1尺、長さ2丈8尺～3丈を1反とし、綿布では幅9寸5分、長さ2丈8尺を1反とした（いずれも鯨尺による）。