Water Tank Fire Reserve Calculator
Enter flow rate, duration, and safety factor to instantly calculate the minimum fire water reserve tank volume in liters, cubic meters, and US gallons.
Tank Sizing Inputs
Selecting a preset fills the flow rate field. You can still edit it.
NFPA 13 defaults: Light 30 min · Ordinary 60–90 min · Extra 90–120 min
1.00 (none)
1.25 (recommended)
1.50 (conservative)
Minimum Reserve Volume
Enter flow rate and duration, then click Calculate.
Minimum Tank Capacity
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liters
Cubic Meters
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m³
US Gallons
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US gal
Calculation Breakdown
Flow rate (L/min)
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Duration (min)
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Base volume (L/min × min)
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Safety factor
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Minimum reserve
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Summary
Enter flow rate, duration, and safety factor to instantly calculate the minimum fire water reserve tank volume in liters, cubic meters, and US gallons.
How it works
- Select the occupancy hazard class or enter a custom flow rate directly.
- Choose your preferred unit — L/min or GPM.
- Enter the required fire-fighting duration in minutes (NFPA 22 minimum is typically 30–120 min).
- Adjust the safety factor (default 1.25, i.e. 25% reserve margin).
- The calculator multiplies flow rate × duration × safety factor and converts to liters, m³, and US gallons.
Use cases
- Size a gravity or pressure tank for a standalone sprinkler system.
- Verify that an existing storage tank meets NFPA 22 reserve requirements.
- Estimate tank capacity early in the design phase for cost budgeting.
- Compare L/min vs. GPM inputs when working with mixed-standard documentation.
- Determine the extra reserve margin needed for high-hazard industrial occupancies.
- Support fire-protection engineering reports and authority-having-jurisdiction (AHJ) submissions.
Frequently Asked Questions
Last updated: 2026-07-24 ·
Reviewed by Nham Vu