Calculator Inputs
Use actual measured weight whenever available. Leave weight blank only when you want an age-based estimate.
Example Data Table
Sample child case to illustrate the calculator layout and output style.
| Field | Example Value | Example Output |
|---|---|---|
| Age | 6 years | Age-based airway formulas available |
| Weight | 20 kg | Used for fluids, EBV, and tidal volume |
| Fasting duration | 6 hours | NPO deficit = 360 mL |
| ETT sizing | Age 6 years | Uncuffed 5.5 mm, cuffed 5.0 mm |
| Maintenance fluid | 20 kg child | 60 mL/hr |
| Estimated blood volume | 75 mL/kg category | 1500 mL |
| Maximum allowable blood loss | Hct 36% to 25% | 458.33 mL |
| Tidal volume range | 20 kg child | 120 to 160 mL |
Formula Used
- Weight estimate: under 1 year = (months / 2) + 4; age 1 to 5 = (2 × age) + 8; age 6 to 12 = (3 × age) + 7.
- Maintenance fluid: 4-2-1 rule. First 10 kg × 4 mL/kg/hr, next 10 kg × 2, each kilogram above 20 × 1.
- NPO deficit: maintenance rate × fasting hours.
- Deficit replacement plan: 50% in hour one, 25% in hour two, 25% in hour three.
- ETT size: uncuffed = age/4 + 4; cuffed = age/4 + 3.5.
- Oral ETT depth: by age after 2 years = age/2 + 12; comparison check = 3 × uncuffed tube size.
- Estimated blood volume: weight × category factor. This page uses 95, 85, 80, 75, or 70 mL/kg depending on selected group.
- Maximum allowable blood loss: EBV × (starting hematocrit − target hematocrit) ÷ starting hematocrit.
- Tidal volume range: 6 to 8 mL/kg for a quick planning estimate.
- Crystalloid bolus range: 10 to 20 mL/kg.
How to Use This Calculator
- Enter the patient age and choose months or years.
- Enter the actual body weight if known. If not, leave it empty to use age-based estimation where available.
- Provide fasting duration, starting hematocrit, and target hematocrit.
- Select a blood volume category or leave the automatic option selected.
- Press Calculate to show results above the form.
- Review airway estimates, fluids, deficit replacement, EBV, ABL, and tidal volume range.
- Use the CSV or PDF buttons to export the calculated summary.
- Confirm all figures with local protocols, equipment markings, and clinical judgment before any patient care decision.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates weight when needed, airway tube sizes, oral tube depth, LMA size, maintenance fluids, fasting deficit, crystalloid bolus range, estimated blood volume, allowable blood loss, and tidal volume range.
2) Should I enter actual weight or use the estimate?
Enter actual weight whenever possible. Age-based equations are practical backups, but measured weight is more reliable for fluid planning, blood volume estimation, equipment selection, and any drug dosing done elsewhere.
3) Are age-based ETT formulas exact?
No. They are starting estimates. Always confirm airway size and depth with direct assessment, capnography, leak evaluation, auscultation, chest movement, and tube markings according to your usual clinical process.
4) Why is the fasting deficit split 50%, 25%, and 25%?
That split is a traditional teaching method for replacing the calculated NPO deficit over the first three hours. Some teams modify this plan depending on case type, fasting history, and patient condition.
5) When is maximum allowable blood loss shown?
It is shown when the target hematocrit is lower than the starting hematocrit. If the target is not lower, the calculator avoids presenting a misleading allowable blood loss value.
6) Does this page calculate drug doses?
No. It intentionally avoids medication dosing. Drug selection and dose preparation should come from your approved pediatric anesthesia references, local policies, and independent clinical verification.
7) Can I use it for neonates and premature infants?
Yes, but with extra caution. The page includes neonatal and premature blood volume categories, while age-based weight and airway estimates should still be checked closely against direct clinical assessment and local neonatal practice.
8) What is the best use for the chart and downloads?
The chart helps compare outputs visually. The CSV and PDF exports are useful for documentation, review, and planning, but they should never replace bedside reassessment or formal charting standards.