How do I calculate the volume of liquid in a horizontal cylindrical tank?

For a horizontal cylinder, the volume of liquid depends on the fill depth, diameter, and length. The formula uses a circular segment calculation: V = L x (R squared x arccos((R-h)/R) - (R-h) x sqrt(2Rh - h squared)), where R is the radius, h is the liquid depth, and L is the tank length. This calculator does the math for you.

How many gallons are in a standard 1000-gallon UST?

A standard 1,000-gallon underground storage tank is typically 48 inches in diameter and 128 inches long (horizontal cylinder). The actual capacity may vary slightly by manufacturer. Use this calculator with your tank's actual dimensions for precise volume.

Tank Volume Calculator

Calculate the total capacity and current volume of liquid in a tank based on dimensions and fill level. Supports horizontal cylinders (most common for ASTs and USTs), vertical cylinders, and rectangular tanks.

Tank Shape

Dimensions

Liquid Level (depth from bottom)

Common Tank Sizes (Reference)

Aboveground Storage Tanks (ASTs): 275 gal (48"D x 27"W x 44"L), 330 gal (48"x30"x48"), 500 gal (48"x38"x60"), 1,000 gal (48"x48"x96"), 2,500 gal (64"x64"x120"), 10,000 gal (96"x96"x210")

Underground Storage Tanks (USTs): 550 gal (48"D x 72"L), 1,000 gal (48"D x 128"L), 2,000 gal (64"D x 120"L), 4,000 gal (64"D x 240"L), 6,000 gal (96"D x 160"L), 8,000 gal (96"D x 213"L), 10,000 gal (96"D x 267"L), 12,000 gal (96"D x 320"L)

55-gallon drum: 22.5" diameter x 33.5" height. 275-gallon tote (IBC): 45"L x 45"W x 46"H (inner dimensions vary). 330-gallon tote: 45"L x 45"W x 53"H.

When You Need Tank Volume Calculations

Accurate tank volume measurements matter for more than inventory control. Several regulatory scenarios require documented tank capacity and current volume.

SPCC planning. Capacity is one part of applicability. EPA explains the storage thresholds, exclusions, and discharge-potential conditions in its SPCC applicability guidance.

Waste accumulation. Volume alone does not establish generator compliance. Federal LQGs have no accumulation quantity limit but must meet applicable conditions, including time limits. See EPA's generator summary.

Containment. SPCC bulk storage uses the largest container plus sufficient precipitation freeboard. There is no universal 110% rule. Our containment tool covers the separate basic comparison in 40 CFR 264.175, not a complete engineered design.

Measurement limits. These ideal-shape estimates do not replace calibrated tank charts, required leak detection, or a release investigation. Verify internal dimensions, end shape, and measurement uncertainty before relying on the result.

How This Calculator Handles Different Tank Shapes

Horizontal cylinders are the most common form for USTs and above-ground diesel or gasoline tanks. The liquid volume at partial fill is a non-linear function of level because the tank cross-section is a circular segment. This calculator uses the exact circular segment formula, not a linear approximation.

Vertical cylinders (common for chemical storage and water tanks) have linear volume-to-level conversion: volume equals pi times radius squared times liquid height.

Rectangular tanks (process tanks, day tanks, many IBCs) are the simplest: length times width times liquid depth. Output is given in both gallons and cubic feet.

Need containment sizing? Use our Containment Volume Calculator for RCRA and SPCC secondary containment requirements. Reporting a spill? Check the State Reporting Directory and RQ Calculator.