About 2/3 of all body fluid is within cells and intracellular compartments. Body fluids (or biofluids) are This is divided between intracellular fluid (ICF) and extracellular fluid (ECF) in a 2 : 1 ratio. Intracellular fluid is within cells and intracellular compartments, while extracellular includes the interstitial fluid (between cells) and the vascular fluid (blood).