Oval Tank Volume Calculator
Work out the volume and capacity of a horizontal oval tank — in US gallons, imperial gallons, litres, cubic feet and cubic metres. This one page covers two geometries that people both call “oval”: the obround/stadium shape and the true ellipse. Enter the width, height and length, and switch the shape selector to match your tank.
Tank volume calculator
Two shapes, one page: oval (obround) vs true elliptical
“Oval tank” is used loosely for two genuinely different cross-sections, and they do not have the same volume:
- Oval / obround / stadium — a rectangle with a semicircle on each end. Seen end-on, it has straight, parallel sides joined by rounded ends, like a running track. This is the calculator’s default, “Horizontal oval (stadium)”.
- True elliptical — a smooth, continuously curved ellipse with no straight sections at all. If your tank is a true ellipse, switch the shape selector to “Horizontal true elliptical”.
Both are horizontal tanks here: the oval is the cross-section and the tank runs along its length. The calculator defaults to the stadium oval; use the “Tank shape” dropdown to change to the true elliptical shape if that matches your tank.
Which oval shape do I have?
Look at the end of the tank. If the top and bottom (or the two sides) are flat and parallel with rounded ends, it is an obround/stadium oval. If the outline curves smoothly the whole way around with no flat sections, it is a true ellipse. When in doubt, measure the overall width and height: on a stadium tank the straight section is exactly width − height long, so if there is a clear flat run, it is obround.
Oval / obround (stadium) tank volume formula
For a stadium tank, take the semicircle radius r = height / 2 and the straight-section width a = width − height. The cross-sectional area is a circle (the two semicircular ends) plus a rectangle (the straight middle), so the oval tank volume formula is:
Because the straight section is width − height, the width must be larger than the height for a true obround — if width equals height it is simply a horizontal cylinder.
True elliptical tank volume formula
For a true ellipse of width w and height h, the cross-sectional area is π × w × h / 4, so the volume is:
This is different from a stadium oval and from a cylinder with elliptical end-caps. For the derivations and sources behind every formula on this site, see the methodology page.
Partial fill and oval tank volume charts
Both oval shapes lie on their side, so — like a horizontal cylinder — the liquid depth and volume are not proportional. Near the middle of the tank an inch of depth adds the most volume; near the top and bottom it adds the least. The stadium oval is handled as a horizontal cylinder (using the height as its diameter) plus a rectangular middle section, while the true ellipse is handled as a circular segment scaled to the ellipse — both exact. To build an oval tank volume chart, enter your dimensions above, turn on “Calculate partial fill”, and step the liquid level through each depth.
Worked examples
Take an oval tank with width 6 ft, height 4 ft and length 8 ft.
- Obround / stadium: r = 4 / 2 = 2 ft and a = 6 − 4 = 2 ft. Area = π × 2² + 2 × 2 × 2 = 12.566 + 8 = 20.566 ft². Volume = 20.566 × 8 = 164.5 ft³ ≈ 1,231 US gallons (≈ 4,659 litres).
- True elliptical (same box): Area = π × 6 × 4 / 4 = 18.85 ft². Volume = 18.85 × 8 = 150.8 ft³ ≈ 1,128 US gallons (≈ 4,270 litres). The ellipse holds less than the stadium oval for the same overall width and height, because it has no straight middle section.
- Half full (liquid depth = 2 ft, half the height): both shapes are symmetric about the mid-height, so each holds exactly half its own total at half depth — about 615 and 564 US gallons respectively.
Enter these numbers in the calculator above, switching the shape selector between the stadium and elliptical options, to confirm the figures and read imperial gallons, litres, cubic feet and cubic metres at the same time.
Units and gallons
Results appear at once in US gallons, imperial (UK) gallons, litres, cubic feet and cubic metres, plus optional petroleum barrels. One US liquid gallon is 231 cubic inches ≈ 3.785 litres, while one imperial gallon ≈ 4.546 litres, so both are shown to avoid ambiguity. Enter inside dimensions for the closest estimate of liquid capacity.
Other tank shapes
For round tanks, use the horizontal cylindrical or vertical cylindrical tank volume calculators. For capsule, rectangular, cone-bottom and cone-top tanks, the main tank volume calculator handles every supported tank shape with full and partial-fill results.
Frequently asked questions
How do you calculate the volume of an oval tank?
It depends on the exact cross-section. An oval/obround (stadium) tank is a rectangle capped by two semicircles, with volume V = (πr² + 2ra) × length, where r is half the height and a is width minus height. A true elliptical tank has a genuine ellipse cross-section, with volume V = π × width × height × length / 4. Pick the matching shape in the calculator above and it does the rest.
What is the difference between an oval tank and an elliptical tank?
An oval (obround or “stadium”) tank has two flat, parallel straight sides joined by semicircular ends — its cross-section looks like a running track. A true elliptical tank is a smooth, continuously curved ellipse with no straight sections. People call both “oval,” but they are different shapes with different volumes, so this page handles each separately.
Which oval shape do I have?
Look at the cross-section end-on. If you can see straight, parallel top and bottom (or sides) with rounded ends, it is an obround/stadium oval — use “Horizontal oval (stadium)”. If the outline curves smoothly all the way around with no flat sections, it is a true ellipse — switch the shape selector to “Horizontal true elliptical”.
What is the oval (stadium) tank volume formula?
For an obround/stadium tank, take the semicircle radius r = height / 2 and the straight width a = width − height. The cross-sectional area is πr² + 2ra, and the volume is that area times the length: V = (πr² + 2ra) × length. This is why the width must be larger than the height — the difference is the straight section.
What is the true elliptical tank volume formula?
For a true ellipse with width w and height h, the cross-sectional area is π × w × h / 4, so the volume is V = π × w × h × length / 4. Note this is different from a stadium oval and from a cylinder with elliptical end-caps.
Is an oval tank volume chart linear?
No. Like a horizontal cylinder, an oval tank lying on its side fills as a curved relationship between depth and volume, so a dipstick chart is not evenly spaced. To build an oval tank volume chart, enter your dimensions above, turn on partial fill, and step the liquid level through each depth you need.
Does this calculator handle vertical oval tanks?
This page models horizontal oval tanks — ones lying on their side, where the oval is the cross-section and the tank runs along its length. A vertical oval tank standing on end uses a different fill model and is not the focus here. For upright round tanks, use the vertical cylindrical tank volume calculator instead.