Calculating your hourly maintenance fluid is straightforward once you know the Maintenance Fluid Calculator (4-2-1 Rule) formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Maintenance Fluid Calculator (4-2-1 Rule).
What is Maintenance Fluid Calculator (4-2-1 Rule)?
The Maintenance Fluid Calculator (4-2-1 Rule) calculation tells you your hourly maintenance fluid from a few simple inputs. The figure you are solving for here is the hourly maintenance fluid.
The Maintenance Fluid Calculator (4-2-1 Rule) formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Body weight — a value measured in kg. Example: 25 kg.
How to calculate it step by step
- Write down the body weight (for example, 25 kg).
- Apply the formula above to get your hourly maintenance fluid.
- Double-check the result with the Maintenance Fluid Calculator (4-2-1 Rule).
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Body weight | 25 kg |
| Hourly maintenance fluid | 65.0 |
| Daily maintenance fluid | 1,560 |
With body weight of 25 kg, the hourly maintenance fluid works out to 65.0.
Example 2
With body weight of 50 kg, the hourly maintenance fluid works out to 90.0.
| Result | Value |
|---|---|
| Hourly maintenance fluid | 90.0 |
| Daily maintenance fluid | 2,160 |
Example 3
With body weight of 13 kg, the hourly maintenance fluid works out to 46.0.
| Result | Value |
|---|---|
| Hourly maintenance fluid | 46.0 |
| Daily maintenance fluid | 1,104 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
- These figures are general estimates, not medical advice — check with a qualified professional before acting on them.
Prefer not to do the maths by hand? — the Maintenance Fluid Calculator (4-2-1 Rule) does it instantly, for free, with the formula and a worked example built in.
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