# What is the maintenance fluid rate?

Calculates the maintenance fluid volume per day by the Holliday-Segar method and the hourly rate by the 4-2-1 rule from body weight.

- Page: https://www.acalculator.org/health/maintenance-fluid-calculator
- JSON spec: https://www.acalculator.org/health/maintenance-fluid-calculator.json
- Version: 2c07e2843743

## Default answer

Example with the default inputs (Weight 33.0693393277316 lb): The maintenance fluid is 1,250 mL per day, or 50 mL per hour by the 4-2-1 rule.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| weight | Weight | Body weight, 3 kg (6.6 lb) or more. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| daily | Per day (Holliday-Segar) | Maintenance fluid in mL per day: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10, 20 mL/kg above 20 kg. |
| hourly | Per hour (daily ÷ 24) | The daily volume spread over 24 hours, in mL per hour, to 1 decimal. |
| rule421 | Per hour (4-2-1 rule) | The 4-2-1 rule: 4 mL/kg/h for the first 10 kg, 2 for the next 10, 1 above 20 kg, to 1 decimal. |

## Method

Per day: 100 mL/kg for the first 10 kg + 50 mL/kg for 10 to 20 kg + 20 mL/kg above 20 kg. Per hour (4-2-1): 4 mL/kg + 2 mL/kg + 1 mL/kg over the same bands.

## Assumptions

- The Holliday-Segar method estimates water needs from calories burned; it gives a volume, not a fluid type.
- Newborns in the first weeks of life and people with kidney, heart, or hormone disorders need other rules.
- The daily volume is rounded to a whole mL and each hourly rate to 1 decimal, halves up.

## Worked examples

1. weight = 8 gives daily = 800, hourly = 33.3, rule421 = 32. Source: Holliday and Segar 1957: 100 × 8 = 800 mL/day.
2. weight = 15 gives daily = 1,250, hourly = 52.1, rule421 = 50.
3. weight = 30 gives daily = 1,700, hourly = 70.8, rule421 = 70.
4. weight = 70 gives daily = 2,500, hourly = 104.2, rule421 = 110.
5. weight = 9.071847 gives daily = 907, hourly = 37.8, rule421 = 36.3.

## FAQ

### What is the Holliday-Segar method?

Holliday and Segar (1957) linked water needs to the calories a child burns. Their rule: 100 mL per kg per day for the first 10 kg of body weight, 50 mL per kg for the next 10 kg, and 20 mL per kg for each kg above 20. A 15 kg child gets 1,000 + 250 = 1,250 mL a day.

### What is the 4-2-1 rule?

The hourly form of the same idea: 4 mL per kg per hour for the first 10 kg, 2 mL per kg for the next 10 kg, and 1 mL per kg above 20 kg. For weights over 20 kg this is 60 mL/h plus 1 mL/h per kg above 20. It is slightly different from the daily volume divided by 24, and the page shows both.

### Does the calculator say which fluid to give?

No. It gives a volume only. The 2018 American Academy of Pediatrics guideline recommends isotonic fluids for most children who need maintenance IV fluids, but the choice of fluid and rate is a clinical decision.

### Who is this rule not for?

Newborns in the first weeks of life, and anyone with kidney disease, heart failure, severe burns, or a hormone disorder that changes water balance. Their clinicians use other methods.

## Sources

- Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832. https://doi.org/10.1542/peds.19.5.823
- Feld LG, Neuspiel DR, Foster BA, et al. Clinical practice guideline: maintenance intravenous fluids in children. Pediatrics. 2018;142(6):e20183083. https://doi.org/10.1542/peds.2018-3083
- National Institute of Standards and Technology. NIST Special Publication 811, Appendix B (1 lb = 0.45359237 kg). https://www.nist.gov/pml/special-publication-811