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 plans (40 CFR 112). Every oil storage tank over 55 gallons must be documented in your Spill Prevention Control and Countermeasure plan, with total aggregate aboveground storage capacity driving the entire compliance program. A tier of SPCC planning activates at 1,320 gallons aggregate.

UST reporting and leak detection. Underground storage tank owners under 40 CFR 280 must track tank volume monthly as part of Statistical Inventory Reconciliation (SIR) or Automatic Tank Gauging. A 0.2 gallon per hour discrepancy triggers a suspected release investigation.

Hazardous waste accumulation limits. LQGs cannot exceed specific volumes in 90-day accumulation areas. SQGs are capped at 6,000 kg total on site. Tank volume is how you prove compliance.

Secondary containment sizing. RCRA (40 CFR 264.175) requires containment of 10% of total volume or 100% of the largest container, whichever is greater. SPCC requires 110% of the largest single tank. Accurate tank volumes determine the minimum containment your site needs. Our Containment Volume Calculator runs both standards side by side.

Release reporting. When a tank fails, you need to know the release volume fast to determine CERCLA reportable quantity status and state notification obligations. A partial-fill estimate based on level readings and this calculator gets you a reportable number within minutes.

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.