Pediatrics
Pediatric maintenance fluids calculator
Calculate a child’s baseline maintenance IV fluids from weight — the 4-2-1 rule for the hourly rate and the equivalent 100-50-20 (Holliday-Segar) rule for the daily volume — and see the full tiered setup behind the answer, not just the number. Free, no signup, runs in your browser.
Interactive calculator
Pediatric maintenance fluid calculator
Enter a child’s weight — in kilograms or pounds — to calculate the maintenance IV fluid rate with the 4-2-1 rule and the equivalent daily volume with the 100-50-20 (Holliday-Segar) rule, and see the worked setup below. Results update as you type.
Result
Enter a weight to see the maintenance rate and the worked setup.
For education and practice only. This computes baseline maintenance fluids only — a dehydrated or acutely ill child needs a fluid deficit and ongoing losses added on top. Verify every fluid order and independently double-check before administering.
How it works
The 4-2-1 rule and the 100-50-20 rule
These are two forms of the Holliday-Segar method — the standard way to estimate a child’s baseline maintenance fluids. Both build the total from weight tiers: the first 10 kg gets the most fluid per kilogram, and each kilogram above 20 kg gets the least. The hourly 4-2-1 rate is the daily 100-50-20 volume divided by 24 (approximately).
Hourly rate — the 4-2-1 rule
4 mL/kg/hr (first 10 kg) + 2 (next 10 kg) + 1 (each kg > 20)
Give 4 mL/kg/hr for the first 10 kg of body weight, plus 2 mL/kg/hr for the next 10 kg (11–20 kg), plus 1 mL/kg/hr for each kilogram above 20 kg. Add the tiers for the total mL/hr.
Daily volume — the 100-50-20 rule
100 mL/kg/day (first 10 kg) + 50 (next 10 kg) + 20 (each kg > 20)
Give 100 mL/kg/day for the first 10 kg, plus 50 mL/kg/day for the next 10 kg, plus 20 mL/kg/day for each kilogram above 20 kg. Divide the daily total by 24 to cross-check the 4-2-1 rate.
Worked example
A maintenance-fluid calculation, step by step
The patient
A child who weighs 26 kg. What are the maintenance fluids by the 4-2-1 and 100-50-20 rules?
Hourly setup (4-2-1)
- 1. First 10 kg: 10 × 4 = 40 mL/hr.
- 2. Next 10 kg: 10 × 2 = 20 mL/hr.
- 3. Remaining 6 kg: 6 × 1 = 6 mL/hr.
- 4. Total: 40 + 20 + 6 = 66 mL/hr.
Daily setup (100-50-20)
- 1. First 10 kg: 10 × 100 = 1000 mL/day.
- 2. Next 10 kg: 10 × 50 = 500 mL/day.
- 3. Remaining 6 kg: 6 × 20 = 120 mL/day.
- 4. Total: 1000 + 500 + 120 = 1620 mL/day.
Answer: 66 mL/hr, or 1620 mL/day.
Reading the result
The two rules should roughly agree. Dividing the daily volume by 24 gives 1620 ÷ 24 = 67.5 mL/hr, close to the 66 mL/hr from the 4-2-1 rule. The small difference is expected — the two rules are approximations of each other, not identical formulas.
Enter 26 kg in the calculator above to see this exact worked setup returned. Try pounds too — the tool converts (lb ÷ 2.2) and shows the conversion in the steps.
Remember this is the baseline. A dehydrated or septic child needs a fluid deficit and ongoing losses calculated and added on top of this maintenance figure.
Common questions
Pediatric maintenance fluids, explained
Maintenance fluids are the baseline volume of IV fluid a child needs over 24 hours to replace normal, ongoing losses — urine output, stool, sweat, and insensible losses from breathing and the skin — when they cannot meet those needs by mouth. They keep a well, euvolemic child hydrated at a steady state; they are not meant to correct an existing fluid deficit.
The 4-2-1 rule gives the hourly maintenance rate: 4 mL/kg/hr for the first 10 kg of body weight, plus 2 mL/kg/hr for the next 10 kg (11–20 kg), plus 1 mL/kg/hr for each kilogram above 20 kg. For a 26 kg child that is (10 × 4) + (10 × 2) + (6 × 1) = 40 + 20 + 6 = 66 mL/hr.
The 100-50-20 rule (the Holliday-Segar method) gives the daily maintenance volume: 100 mL/kg/day for the first 10 kg, plus 50 mL/kg/day for the next 10 kg, plus 20 mL/kg/day for each kilogram above 20 kg. It is the same tiered idea as 4-2-1, just expressed per day. Dividing the daily volume by 24 gives approximately the hourly 4-2-1 rate — for a 26 kg child, 1620 mL/day ÷ 24 = 67.5 mL/hr, close to the 66 mL/hr from 4-2-1. The small difference is expected because the two rules are approximations of each other.
Fluid and energy needs do not rise in a straight line with body weight — smaller children have a higher metabolic rate and a larger surface-area-to-mass ratio, so they need proportionally more fluid per kilogram. The tiers (4/2/1 per hour, or 100/50/20 per day) approximate this curve: the first 10 kg gets the most fluid per kilogram, and each kilogram above 20 kg gets the least.
No. The 4-2-1 and 100-50-20 rules cover baseline maintenance only. A child who is dehydrated or acutely ill needs more: an estimated fluid deficit and any ongoing abnormal losses (vomiting, diarrhea, fever, drainage) are calculated and given in addition to maintenance. This calculator does not estimate a deficit — it computes the maintenance baseline that a full fluid plan is built on.
Yes. It is completely free, needs no account, and runs entirely in your browser, so it works on a phone. It is a study and practice aid only — every pediatric IV fluid plan requires an independent double-check against the order, the child's clinical status, and institutional policy before administering.
Keep the med-math going
From maintenance rate to the pump
Once you have the maintenance rate in mL/hr, the IV drip-rate calculator turns it into drops per minute for a gravity set. Drill pediatric concepts on the topic page, or explore the other free calculators.
This calculator and all study material on this site are provided for practice and study only. It computes baseline maintenance fluids only, not deficit or replacement volumes. Verify every fluid order before administering.
More free tools
Related calculators
Reach for these alongside this one — the calculations that most often come up together on the wards and in practice questions.
Pediatric Safe Dose Calculator
Check an ordered pediatric dose against the safe mg/kg range and daily maximum.
IV Drip Rate Calculator
Convert an ordered volume and time into gtt/min or mL/hr for any drop factor.
APGAR Score Calculator
Score a newborn's appearance, pulse, grimace, activity, and respiration.
Practice these — free questions
Apply it on real NCLEX-style questions
A calculator hands you the number; the exam makes you reach it under pressure and defend it. Drill Pediatrics questions that put this calculation inside a realistic clinical scenario — each one with a written rationale, so you learn why the answer is right, not just what it is. That explained-rationale practice is what sets us apart from a bare calculator.
Free · no spam
Get a free high-yield NCLEX question every week
One carefully written practice question plus a short study tip, emailed weekly. Unsubscribe anytime — we never share your address.