Total Body Water Calculator

Written by Great Medico

Updated September 24, 2026 •2 min read

Share Print Save

Fluid and electrolyte decisions often start with a small equation and a careful unit check. Total Body Water Calculator makes that calculation visible without pretending the number replaces bedside assessment.

What this calculator does

Total Body Water Calculator uses Sex, Age, Height, and Weight to calculate estimated total body water. Where supported, it also shows Weight equivalent and Percent of body weight so the primary result is easier to check. It follows the exact field flow and engine behavior in this plugin rather than describing a different calculator with the same name. Fluid and electrolyte formulas are sensitive to units, timing, ongoing losses, kidney function, and rapidly changing physiology. They are most useful as structured estimates alongside repeat measurements and bedside assessment.

How to use it

Enter or select Sex, Age, Height, and Weight. Use the units offered by the calculator and keep paired laboratory or treatment values from the same clinical episode whenever the formula assumes that. If an entry is unknown, do not substitute a guess simply to obtain a number.

How the calculation works

For males, total body water is estimated with 2.447 − 0.09516 × age + 0.1074 × height(cm) + 0.3362 × weight(kg). For females, it uses −2.097 + 0.1069 × height(cm) + 0.2466 × weight(kg). The tool also expresses the result as a percentage of body weight.

Example

Using the sample values prefilled in this calculator, the primary result is 42.65 L (Estimated total body water), Weight equivalent is 42.65 kg, and Percent of body weight is 56.9%. This example demonstrates the plugin’s own calculation path; replace the sample inputs with verified values before interpreting a real result.

How to interpret the result

Read the output as estimated total body water from the implemented formula. Compare it with measured values, volume status, ongoing inputs/losses, and serial trends; treatment decisions should not rely on the calculator in isolation.

Limitations and notes

Fluid and electrolyte formulas are sensitive to units, timing, ongoing losses, kidney function, and rapidly changing physiology. They are most useful as structured estimates alongside repeat measurements and bedside assessment. During active treatment, repeat laboratory measurements and clinical response can rapidly make an earlier calculated estimate outdated.