Fluids & Resuscitation

Maintenance Fluids (4-2-1 Rule) Calculator

Hourly maintenance fluid by the 4-2-1 rule from weight; a starting point, not a substitute for watching intake, output and electrolytes.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Turn on JavaScript to use this calculator, or open it in the web app.

Formula

1st 10kg: 4 mL/kg/hr
2nd 10kg: 2 mL/kg/hr
Remaining kg: 1 mL/kg/hr

Shortcut for >20kg: Weight in kg + 40

How it is used

• Used to calculate basal fluid requirements for patients NPO without significant ongoing losses.
• Not meant for resuscitation in shock or severe dehydration.

Same formula as the app. Open it in the web app.

Related one-pagers

• BurnsChildren have more surface area per kilogram, thinner skin that burns deeper at lower temperatures, small glycogen stores and narrow airways: 1 mm of edema in a 4 mm infant trachea halves the radius and raises resistance 16-fold. Formula resuscitation starts at smaller burns (over 10% TBSA in JTS 2025, 15% in some protocols) at 3 mL/kg/%TBSA plus untitrated maintenance D5LR by the 4-2-1 rule; the dextrose cutoff is under 30 kg in ABA-based protocols, under 13 years in JTS. JTS checks electrolytes every 8 hours for the first 72 hours.
• Shock Types at a Glance
• Sepsis and Septic Shock Bundle

Related calculators

• Intake and Output Balance
• Parkland Formula

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.