What is a Fuel Tank Capacity Calculator?
A fuel tank capacity calculator determines the gross volume, usable fuel capacity, and safe fill limits for mobile and stationary fuel tanks. Sizing fuel capacity accurately helps determine available fuel storage while supporting proper filling practices and reducing the risk of overfilling.
See fuel tank spill and overfill requirements in the EPA Release Prevention for Underground Storage Tanks guide.
Fuel Tank Capacity Formulas
Cylindrical Tank Capacity:
Total Capacity = π × (Diameter / 2)² × Length
Rectangular Vault Capacity:
Total Capacity = Length × Width × Height
Usable Net Operating Capacity (95% Safety Rule):
Net Capacity = Gross Volume × 0.95
Step-by-Step Fuel Sizing Process
- Identify Tank Shape: Determine if your fuel vessel is cylindrical or rectangular.
- Measure Dimensions: Measure internal length, width, height, or diameter.
- Calculate Gross Volume: Apply geometry formulas to find total cubic capacity.
- Account for Expansion: Deduct 5% expansion ullage volume for safe operations.
Practical Calculation Walkthrough
For a cylindrical generator fuel tank measuring 5 ft diameter and 12 ft length:
Radius r = 5 / 2 = 2.5 ftGross Volume = 3.14159 × (2.5)² × 12 = 235.62 ft³Gross Capacity in Gallons = 235.62 × 7.48052 ≈ 1,762.56 US GallonsNet Usable Fuel (95%) = 1,762.56 × 0.95 ≈ 1,674.43 US Gallons
Fuel Storage Sizing Reference Chart
| Tank Sizing | Dimensions | US Gallons | Litres |
|---|---|---|---|
| 275 Gal Heating Tank | 27" × 60" | 275 gal | 1,041 L |
| 500 Gal Fuel Vault | 48" × 72" | 500 gal | 1,893 L |
| 1,000 Gal Generator Tank | 48" × 144" | 1,000 gal | 3,785 L |
| 2,000 Gal Fleet Cistern | 64" × 144" | 2,000 gal | 7,571 L |
| 10,000 Gal Commercial UST | 96" × 324" | 10,000 gal | 37,854 L |
Safety Guidelines & Regulatory Compliance
Fuel storage installations must include secondary containment bunding capable of holding at least 110% of the primary tank volume to prevent environmental contamination in case of tank failure.
Fuel Expansion & Ullage Calculations
Fuel expands significantly when ambient temperatures rise. Fuel storage tanks should never be filled to 100% capacity; leaving a 5% to 10% vapor space (ullage) prevents pressure buildup and accidental fuel venting.