Tank Volume Calculator

Measure the inside dimensions of the tank, pick the shape, and apply the matching formula. A vertical cylinder is π × r² × height; a rectangle is length × width × height; a horizontal cylinder is π × r² × length. This calculator does the geometry for you and converts the result into US gallons, imperial gallons, liters, cubic feet and cubic meters in one step — and it handles the hard cases (partial fill, dished heads, tilt) that hand formulas ignore.

A standard 275-gallon home heating-oil tank measures roughly 60" long with a 27 × 44-inch oval (stadium) cross-section. Its geometric capacity works out to about 268 US gallons — the nameplate rounds up. Because the usable fill stops at about 90% for expansion, expect roughly 240 usable gallons, which is why a "quarter-tank" reading matters more than the sticker.

A horizontal tank's circular cross-section is narrow at the bottom, widest at the middle and narrow again at the top. At exactly half depth the tank is 50% full by symmetry — but at a quarter depth it typically holds only 19–20% of capacity, and at three-quarters depth about 80%. Volume follows a non-linear curve, which is precisely what the dip chart below tabulates.

A dip chart (also called a strapping or calibration table) lists liquid depth readings against the volume they represent, from empty to full. Field staff dip the tank with a gauge stick, read the wet depth, and look up the volume instantly — no math on site. Set an increment (every inch, centimeter or 5% of depth) and the generator above prints the full table, with the filled volume, percentage and remaining ullage for each row.

Inside dimensions. The calculator assumes the numbers you enter are internal measurements — capacity is defined by the wetted space. If you can only measure the outside, subtract twice the wall thickness from each dimension (and remember that steel tanks commonly lose a little more to internal corrosion scale over their life). A half-inch of wall on a 36-inch diameter tank overstates capacity by about 5%.

Flat heads are simple closing plates and add no volume. Hemispherical heads are half-spheres (depth = D/2) and add the most: together they contribute a full sphere's worth of volume. 2:1 elliptical heads are half-ellipses with depth = D/4 — the ASME pressure-vessel standard — and add exactly half of what hemispherical heads do. Torispherical (dished, ASME F&D style) heads are shallower still and add roughly 0.081 × D³ per head. The head panel above reports the head volume separately from the body.

Pick the liquid and the calculator multiplies the volume by its density. Water weighs 8.35 lb per US gallon (1 kg per liter), diesel about 7.1 lb/gal, gasoline about 6.2 lb/gal and milk about 8.6 lb/gal. A 275-gallon tank of heating oil (SG ≈ 0.85) holds roughly 1,950 lb — close to a ton — which matters for stands, pads, floors and delivery trucks.

Yes — on horizontal tanks it can. Installers deliberately slope tanks toward the drain end, and even a 1–2° tilt shifts the depth-to-volume relationship noticeably near the ends of the range. At 2° over a 60-inch tank the ends differ by more than two inches of liquid depth. Enable the tilt correction above, enter the angle (or the end-to-end drop) and where you took the dip reading, and the engine integrates the depth along the whole length instead of assuming a level tank.

One cubic foot holds 7.48052 US gallons (and 28.317 liters), so multiply cubic feet by 7.48052. Going the other way, divide gallons by 7.48052. For oil barrels, one 42-gallon barrel is 5.615 cubic feet. The results panel shows every volume unit at once, so no manual conversion is needed.

Ullage is the unfilled space above the liquid in a tank — the room left for thermal expansion, vapour and sloshing. Fuel deliveries typically stop around 90–95% full to preserve it. The results panel reports ullage in every volume unit, and the dip chart's final column tracks it at every depth so you can see exactly how much more the tank can take at any reading.

Volume is the pure geometric space inside the tank — what the formulas compute from your dimensions. Capacity is what the tank can usefully hold in practice, which is often lower: freeboard at the top, internal baffles, fittings, pumps and the manufacturer's fill limit all eat into it. When comparing tanks for a project, always check whether a published figure refers to total geometric volume or rated (usable) capacity, and confirm which one your local code requires.

Measure in centimeters and the product of your dimensions is cubic centimeters: divide by 1,000 for liters. If you measure in meters, multiply cubic meters by 1,000. Working in inches, divide cubic inches by 61.024 to get liters; working in feet, multiply cubic feet by 28.317. The converter section below does all of these conversions live, and the results panel shows liters alongside US and imperial gallons automatically.

The geometry is identical to any other tank — enter the internal dimensions and the calculator returns the volume regardless of what the tank holds. What differs is how the required size is determined. Septic tank sizing is set by your local health department based on occupancy and wastewater flow, and chemical storage depends on the chemical's properties, secondary containment and applicable codes. Use the calculator to convert proposed dimensions into a volume figure, then confirm that figure against the authority having jurisdiction or a qualified engineer before purchasing.

Never more than 80% of its water capacity — this is a legal requirement, not a suggestion. Liquid propane expands roughly 1.5% for every 10 °F of temperature rise, and the 20% headspace prevents hydrostatic overpressure on a hot day. That is why a '500-gallon' propane tank holds about 400 gallons of propane when full, and why the common tank sizes chart below shows a working fill of 80% for every ASME propane vessel.

Yes — pick the shape and the engine applies the exact geometry for it. For cylindrical tanks the calculator uses πr²h upright and integrates the circular segment when the cylinder lies on its side; for rectangular tanks the volume is simply length × width × height. Each result reports US and imperial gallons alongside liters and cubic meters, so one tool covers fuel, water and chemical storage without switching settings.

Measure in centimetres and litres fall out directly: length × width × height ÷ 1,000. A 120 × 50 × 60 cm rectangular tank holds 360,000 cm³ = 360 L. Working in inches, divide cubic inches by 61.024 — the 48 × 24 × 12 inch box from the formulas section is 13,104 in³ ≈ 215 L. The calculator shows litres next to every gallon figure automatically, so there is no separate conversion step.

For the usual upright round water tank it is V = π × r² × h — the inside radius squared, times π, times the water height. A tank 1.8 m in diameter and 2 m tall holds π × 0.9² × 2 = 5.09 m³ ≈ 5,090 litres (about 1,345 US gallons). Measure the inside radius, keep the units consistent, and stop at the overflow shoulder if the dome does not store water. A round tank lying on its side is different: depth-to-volume becomes non-linear, so switch to the horizontal cylinder mode and the dip chart instead of the one-line formula.

Work backwards from demand. Add up daily use — a family of four typically needs 600–800 litres of water per day, heating oil arrives in fixed delivery increments, and propane is legally capped at 80% fill — multiply by the days of autonomy you want, and you have the target capacity. Enter candidate dimensions in the calculator until the output matches that figure, then check the standard tank sizes chart to find the nearest nameplate model. That turns the tool from a volume converter into a genuine tank size calculator for shopping comparisons.

Weight in pounds equals volume in US gallons × 8.34 × specific gravity. Water is SG 1.00 (8.34 lb/gal), diesel is roughly 0.84 (7.0 lb/gal), gasoline is about 0.74 (6.2 lb/gal). The calculator's liquid-weights panel multiplies the current filled volume by the selected density and reports the result in lb, kg and metric tons — so you get both the empty-tank shell weight (from the steel/SS mass) and the full-tank contents weight from one input. For empty steel tanks, estimate the shell mass as surface area × wall thickness × 490 lb/ft³.

Fill time in minutes = tank volume in gallons ÷ fill rate in gallons per minute. Drain time uses the same formula — but only if the drain rate is constant. Gravity draining from a tank slows as the level drops, so the average drain rate is roughly half the initial flow: use V ÷ (2 × Q₀) where Q₀ is the flow rate when the tank is full. The calculator does not compute fill/drain time directly, but it gives you the volume to divide by your pump's GPM rating.

Yes for simple shapes. For a vertical cylinder: r = √(V ÷ (π × h)) — pick a height and solve for radius. For a rectangle: any two dimensions can be derived from V, but you need to know the ratio between them (e.g., width is 2 × height). For horizontal cylinders and shapes with dished heads the algebra is messier — enter candidate dimensions and tweak them against the calculator output until you hit the target capacity.

They are the same document. Strapping (or calibration) table, dip chart, and gauge table all describe the depth-to-volume relationship for a specific tank. Professional tank calibration services produce them by physically strapping a tank with surveyor's tape at each inch level — our generator does the same thing from geometry, which is accurate enough for field use unless your local code requires a certified strap.

Floor area of a cylindrical tank: π × r². Wall surface: π × D × height. Total wetted area of a full tank combines the floor with the wall area. For a partially filled vertical tank the wetted wall area is π × D × f (f = fill height) — the water touches only the submerged wall plus the floor. The calculator returns surface area in the advanced panel for all shapes.

One cubic foot = 7.48052 US gallons = 28.317 liters = 0.1781 oil barrels. One US gallon = 231 cubic inches = 3.785 liters. One oil barrel (42 US gal) = 5.6146 cubic feet = 158.99 liters. The converter section below handles all of these bidirectionally without a manual formula — and every result panel shows every volume unit at once so you never need a separate conversion step.

All three bulge outward from a horizontal cylinder's flat ends, adding volume to the shell. Hemispherical heads are true half-spheres (depth = D/2) and add the most — a full sphere's worth per pair. 2:1 elliptical heads (depth = D/4, the ASME pressure-vessel standard) add exactly half that. Dished heads (ASME F&D style, depth ≈ 0.1 D) add the least. The head-types section below compares them side-by-side and reports each head's contribution separately from the shell.

Because the cross-section is a circle, which is narrow at the bottom, widest at the middle, and narrow again at the top. At 25% depth a horizontal cylinder holds only about 19.6% of its capacity; at 75% depth it holds about 80%. Only at exactly half depth — where the circle is symmetric — does depth equal volume percentage. The dip chart generator tabulates this non-linear curve for whatever shape you pick.