Hounsfield units - scale of HU, CT numbers

The Hounsfield scale of tissue density is based on two values: air as -1000HU (minimum HU value) and water as 0HU. Density of other tissues is related to this range, usually from -1000 to +1000HU (-1024 to 1024 or 3072 depending on the coding of particular vendor). However, the scale by its the definition is open-ended.

Matter Density (HU)
Air -1000
Lung parenchyma (inspirium) -850 to -910
Fat -50 to -100
Water 0
White matter 20 to 30HU
Kidney 20 to 40HU
Spleen 35 to 55HU
Grey matter 37 to 45HU
Blood 45 to 65HU
Liver 45 to 65HU
Hematoma 40 to 90HU
Bone 700 to 3000


1. Buzug TM. Computed Tomography: From Photon Statistics to Modern Cone-Beam CT. Springer; 2008:475
2. Heymsfield S. Human Body Composition. Human Kinetics; 2005
3. Prokop M. Spiral and Multislice Computed Tomography of the Body. Thieme; 2003.