General physiology mnemonic

Rule of fractions for body water

The mnemonic

60-40-20 rule

What each word stands for

  • 60Total body water is about 60% of body weight
  • 40Intracellular fluid is about 40% of body weight
  • 20Extracellular fluid is about 20% of body weight

Why it matters clinically

Fluid replacement and drug distribution depend on these volumes.

Where it stops being reliable

Percentages vary with age, sex and fat content; it gives no values for plasma versus interstitial split.

Teaching aid, still awaiting independent review. Confirm facts in a standard source.

More mnemonics

Common questions

What is the General physiology mnemonic?

60-40-20 rule. It helps you recall: Rule of fractions for body water.

What does "60" stand for?

Total body water is about 60% of body weight

What does "40" stand for?

Intracellular fluid is about 40% of body weight

What does "20" stand for?

Extracellular fluid is about 20% of body weight

What are all the parts of the 60-40-20 rule mnemonic?

60: Total body water is about 60% of body weight; 40: Intracellular fluid is about 40% of body weight; 20: Extracellular fluid is about 20% of body weight.

Which topic does this mnemonic belong to?

It belongs to General physiology in Physiology.

Where does this mnemonic stop being reliable?

Percentages vary with age, sex and fat content; it gives no values for plasma versus interstitial split.

How is this useful clinically?

Fluid replacement and drug distribution depend on these volumes.

How do I make this mnemonic stick?

Say it aloud, write it from memory tomorrow, then again in a week. Then test yourself on a Physiology question about General physiology.

Is this a standard mnemonic?

It is a teaching aid written or adapted by our team. Some resemble ones students share informally. Check any fact that matters in a standard source.