100-50-20 / 4-2-1 Rule for Estimating Maintenance Fluids*
Body weight kg
> ml/24h
ml/h
First 10 kg body weight
100 mL/kg/24h (4mL/kg/h)
Second 10 kg body weight
50 mL/kg/24h (2 mL/kg/h)
Each additional kg body weight
20 mL/kg/24h (1 mL/kg/h)
Example for a 70 kg pt: (10x100)+(10x50)+(50x20) = 2500 mL/24h; (10x4)+(10x2)+(50x1) = 110 mL/h
Quick calculation of maintenance fluid rate in ml/h:
Body weight (kg) + 40;
Example: For 70 kg pt, rate is 70+40 = 110 mL/h; This order may be written as 1/2NS at 110 mL/h x 24 hours
*The values shown assume normal renal function, no CHF, and no edema present.
Care should be exercised in geriatric, thin, frail patients who may require a reduction from calculated value.