Tank volume FAQ

Total volume is πr²L (radius squared × pi × length). For a partly filled tank the liquid forms a circular segment, so you need the segment area × length — our horizontal cylinder calculator does it exactly, and the formula page shows the full derivation.

V(h) = [r²·acos((r−h)/r) − (r−h)·√(2rh−h²)] × L, where h is liquid depth. It’s the circular-segment area times the length — closed-form, spreadsheet-friendly, and explained on the horizontal cylinder formula page.

Be careful which “oval” you have: a true ellipse uses πab×L (our oval calculator), but most home heating-oil tanks are actually obround — flat sides with semicircular ends — which needs different piecewise math on the heating oil tank calculator.

Yes — the cone-bottom calculator handles the conical section (volume grows with the cube of depth there) plus the cylindrical body, in gallons or litres. At 40% depth a typical cone tank holds only about 26% of its volume.

An ellipse is a circle scaled horizontally, so the area is π×a×b and a partial fill is (a/b) times the equivalent circular segment — exact, no approximation. See the elliptical formula page or run it on the oval calculator.

Full sphere is (4/3)πr³; a partial fill uses the spherical-cap formula πh²(3r−h)/3. It’s strongly nonlinear — exactly half the sphere at half depth, but only ~15.6% at quarter depth. The sphere calculator handles both.

Yes — the frustum calculator uses πH(R²+Rr+r²)/3 for the full tank and interpolates the wetted radius for partial fills, covering buckets, hoppers and tapered vats.

An ASME torispherical (F&D) head has no tidy closed form, so we scale the spherical cap by an effective depth (0.1545×D) matched to the standard head volume — worst-case error under 0.06% of a 500-gallon vessel. Details and the error bounds are published; use the propane calculator for dished-head vessels.

A pipe is a horizontal cylinder on its inside diameter: V = π(ID/2)²×L. The pipe volume calculator gives gallons and water weight per length; use the nominal vs actual ID carefully, since schedule changes the bore.

A round stock tank is a vertical cylinder: gallons per inch of depth = π(D/2)² ÷ 231. A 10-ft-diameter tank holds about 587 gallons per foot of depth. Enter your diameter on the vertical cylinder calculator, or print a chart with the dip chart generator.

Yes — volume is L×W×H ÷ 231 for gallons (or ÷1000 for litres from centimetres). The rectangular calculator handles totes, sumps and aquariums at any fill level.

A hemisphere is half a sphere: (2/3)πr³. A capsule (cylinder with two hemispherical ends) combines a cylinder with one full sphere of heads — see the capsule formula or the sphere calculator for the cap math.

Add the cylindrical shell (a circular segment × length) to the two dished heads. Ellipsoidal 2:1 heads scale the spherical cap by ½; ASME F&D heads are shallower. The propane calculator models F&D heads; the formula page shows the method.

It’s the easy one: every slice is the same circle, so volume is exactly linear — πr²h, with a constant gallons-per-inch of πr²÷231. The vertical cylinder calculator covers it.

A sloped or coned bottom holds less near the floor than a flat one. For a conical bottom use the cone-bottom calculator; for a slight slope, approximate with the cone section depth. The key point is that the bottom portion is never linear — don’t use flat-tank gallons-per-inch there.

It is, in any shell that is symmetric about its mid-height — a plain cylinder, a rectangle, an obround. It is not in a cone-bottom, a dished-bottom or a frustum, where the shell holds more at one end than the other. Every chart page states the depth at which half that tank's volume actually sits, so you can check rather than assume.

Because the liquid surface is a chord, and a chord is widest at the centre of the circle. On a 275 horizontal, one inch at 13″ is 11.50 gallons against 6.20 gallons at 27″ — a factor of 1.9. That is why interpolating linearly between two distant chart rows goes wrong.

More than people expect on small or thick-walled tanks. Half an inch of wall on a 48-inch tank removes about 3 % of the cross-sectional area, and therefore 3 % of every reading. Thin steel you can usually ignore; polyethylene at a quarter inch or more you cannot. Measure inside where you can reach.

Typically within 1–3 % of the manufacturer's own chart. The difference is corner radii, internal ribs, plate thickness, fabrication tolerance and tank tilt. That is fine for ordering and reconciliation and is not a calibration — for that a tank must be strapped under ISO 7507-1 or the equivalent API chapters.

Enter your tank’s dimensions and shape in the dip chart generator, pick a step (1″, ½″, 1 cm or 5 cm), and download a laminate-ready PDF converting every depth to volume — with your dimensions printed on each page for field verification.

Yes, but the conversion isn’t linear — the middle inches hold the most. Use a per-tank chart or generate one for your exact size; for straight-walled tanks the gallons-per-inch calculator gives the constant.

The 275 vertical and 275 horizontal chart pages have full inch-by-inch tables and printable PDFs — cross-checked against the Highland Tank gauge book.

Gallons of propane = gauge percent × water capacity. A 500-gallon tank at 38% holds 190 gallons. Remember the gauge reads percent of water capacity and “full” is 80% — the 500 propane chart has the table.

Stick the tank to the bottom, read the wet line, and convert with the chart for your tank’s size and orientation. The 1000-gallon chart covers the common underground cylinder; print it for the field.

For a vertical 48-inch-diameter tank it’s a constant 7.83 gallons per inch (π×24²÷231). For a horizontal 4-foot tank it varies with depth — most at the centerline, least near top and bottom — so use a chart. Try the gallons-per-inch calculator.

Yes — the dip chart generator produces a calibrated strapping chart for any tank from exact geometry, the same math verified against manufacturer gauge books.

Lower a clean stick straight down to the tank bottom, hold it vertical, lift it out and read the wet/dry line — that depth converts to gallons on your chart. The full technique, including water-finding paste, is in the stick method guide.

A strapping (dip) chart tabulates volume at each depth increment using the tank’s exact partial-fill geometry — circular segments for round tanks, piecewise math for obround. Our methodology page documents every formula; the generator builds the chart.

Yes — every calculator here takes a liquid depth and returns volume for the matching shape. Start at the universal calculator, pick your tank, and move the depth slider or type the stick reading.

It depends what an inch is worth on your tank. On a 275 vertical the steepest inch is 7.0 gallons, so an eighth of an inch is under a gallon; on a 12-foot-diameter vertical tank an inch is 70.5 gallons and an eighth is nearly 9. For regulated underground tanks, 40 CFR § 280.43 requires equipment that resolves the full tank height to the nearest one-eighth of an inch.

Two, averaged. The federal manual tank gauging method specifies readings “based on an average of two consecutive stick readings” because a single reading carries more scatter than the chart arithmetic ever will. A quarter inch of scatter is about 1.8 gallons on a 275 vertical.

Yes, and always in the same direction — long. Ten degrees off vertical reads about 1.5 % high; twenty degrees reads 6 % high. An angled fill pipe does not excuse an angled stick; the stick still has to end up vertical inside the tank.

Usually the gauge — float gauges are ±5 % instruments when healthy and worse when sticking. But check your own side first: reading a 275 vertical chart for a horizontal tank is an 83 % error at 12 inches, far bigger than any gauge fault. See chart vs gauge.

Yes. Every chart page has a Download PDF button that produces a one-page field sheet, and the dip chart generator will build one for dimensions that do not match a standard size.

A standard 275 is an obround tank about 27″ wide × 44″ tall × 60″ long (vertical orientation), holding ~267.9 gallons brim-full and filled to ~250. Full specs and weight are on the 275 dimensions page.

If “10 foot” is the diameter, a round stock tank holds about 587 gallons per foot of water depth (π×5²×7.48). A 2-foot-deep fill is ~1,175 gallons. Enter your exact diameter and depth on the vertical cylinder calculator.

A 500-gallon ASME propane tank is about 37.5″ in diameter and ~10 feet long overall including the dished heads. Dimensions, weights and NFPA 58 clearances are on the 500 propane page.

A 3×3×3-foot cube is 27 cubic feet × 7.48 = about 202 gallons. For exact figures on any box dimensions use the rectangular calculator.

Standard IBC totes are 275 and 330 gallons. The bottle is roughly rectangular with rounded corners, so use the molded markings near the bottom and the 275 / 330 tote charts for in-between depths.

Standard rectangular frac (frac/storage) tanks typically hold around 21,000 gallons (500 barrels); a “20K” unit is about 20,000 gallons. Because models vary by manufacturer, confirm against the nameplate — then verify any depth with the rectangular calculator.

About 1,337 cubic feet — for example a vertical cylinder roughly 12 ft in diameter and 12 ft tall, or 10 ft diameter × 17 ft. Manufacturers vary the proportions; the sizes library and calculator let you check any combination.

Common diesel storage runs 100, 250, 500, 1000 gallons and up; transfer tanks are 50–100 gallons. See the tank sizes library for dimensions and the diesel weight page for load planning (500 gallons ≈ 3,525 lb).

In the US, size by bedrooms — 1,000 gallons is the typical 3-bedroom minimum; in India, by users under IS 2470. The septic calculator covers both, but your local health authority’s code governs the final number.

Common steel USTs use 48″ or 64″ diameters: a 64″×108″ holds ~1,500 gallons, 64″×144″ ~2,000. Dimensions and charts for the standard sizes are in the sizes and charts libraries.

Nominal is the trade label — a name, chosen for being round. Geometric is what the stated dimensions actually hold brim-full. Usable is what you can get in and out after ullage, dead volume below the outlet and, for propane, the 80 % filling limit. A “275 gallon” oil tank is 267.9 gallons geometric and about 250 in service.

Because the label is a cage size and the authoritative figure is the rated capacity in the UN marking moulded into the bottle and stamped on the cage, applied under 49 CFR Part 178 Subpart N. That marking also carries the packing group, maximum gross mass and, for regulated use, a retest date.

55 is the rated fill capacity; brim-full is several gallons more, and the difference is deliberate outage for thermal expansion. Modern drums are coded 1A1 (tight head) or 1A2 (removable head) under 49 CFR § 178.504 — the older DOT-17E designation was superseded by those UN standards.

Look for a nameplate first — a UL 80 plate, an ASME nameplate or a UN marking is authoritative where a tape measure is not. Then establish the section by feel, measure inside, and compare against the standard families. The identification guide walks through it.

About 3,525 lb (at ~7.05 lb/gal; the 7.0–7.1 grade range puts it at 3,500–3,550). In a typical skid tank that’s 4,200–4,700 lb gross — beyond a half-ton pickup’s payload. Full breakdown on the 500 gallons of diesel page.

Yes — the thermal expansion calculator computes ΔV = V×β×ΔT with sourced coefficients (diesel 0.00046/°F per Chevron), tells you whether your ullage absorbs the swing, and gives the max safe temperature.

Enough to absorb thermal expansion plus a working margin: heating oil tanks fill to ~90% (a 275 to ~250 gal), and codes/suppliers set the practice. The thermal calculator shows the physics; see also what ullage is. Codes govern over the bare math.

UAN 32% is about 11.06 lb/gal and UAN 28% about 10.65 — so a 275-gallon tote of UAN 32 is over 3,000 lb. Cited figures and a calculator are on the UAN weight page.

Vapor (ullage) space is tank capacity minus liquid volume; for crude, overfill protection follows API 2350, which reserves more than thermal expansion alone requires. Crude density varies widely by grade (6.6–8.1 lb/gal), so we don’t publish a single value — use measured gravity. The thermal/ullage tool covers the expansion math.

Ullage is the empty distance from a top reference down to the surface; sounding (innage) is the liquid depth from the bottom. They sum to the reference height. Every calculator here reports both — see the ullage guide.

Weight = volume × (specific gravity × 8.345 lb/gal). The weight library lists cited densities and gives gallons→pounds/kilograms for 15 liquids; multiply SG by 8.345 for any other fluid.

The thermal expansion tool shows the physics-based fill room and always reports the larger of expansion and a 5% working margin. It’s a screening estimate only — chemical and pressure-tank fill limits are set by codes (NFPA, OSHA, API) that govern over any calculator.

The water alone is about 8,345 lb (1,000 gal × 8.345) — over four tons — plus the tank. Design the slab or stand for it; see the water weight page.

Liquid propane expands far more than fuels — roughly 15× water per degree — which is exactly why NFPA 58 caps the fill at 80% and the float gauge is calibrated to it. You don’t compute LPG ullage yourself; the 80% rule is the answer. Background is on the thermal expansion page.

Exactly 3.785411784 L. The value is exact rather than measured: a US gallon is defined as 231 cubic inches in NIST Handbook 44, and an inch as 2.54 cm by the 1959 International Yard and Pound Agreement, so the litre figure is pure arithmetic. See gallons to litres.

Two independent legal definitions. The UK Weights and Measures Act 1985 fixes the imperial gallon at 4.54609 litres; the US kept the older 231-cubic-inch wine gallon. One imperial gallon is about 1.2 US gallons — a 20 % gap that catches out anyone reading UK, Irish or older Canadian tank specs.

Exactly 42 US gallons for a petroleum barrel — the figure is fixed in 43 CFR § 3174.2 and used throughout EIA statistics. A 55-gallon drum is not a barrel; treating drums as barrels overstates volume by 31 %.

Exact and terminating: gallons to litres, gallons to cubic metres, cubic feet to litres, imperial gallons to litres. Exact but non-terminating: cubic feet to gallons (576/77), gallons to cubic feet (77/576), cubic inches to gallons (1/231), gallons to barrels (1/42). For the second group, divide by the exact factor rather than multiplying by a truncated reciprocal — the conversion library lists them all.

For most tank work, yes. It runs 0.0069 % low against the exact 576/77, which is about 0.7 gallons on a 10,000-gallon tank — far less than the error in measuring the tank.

The conversion does not; the liquid does. Both units are geometric, so 3.785411784 L per gallon holds at any temperature. What changes is how much substance occupies that volume, which is why fuel is traded on volume corrected to 60 °F or 15 °C.

Divide the gallons you have by your own burn rate rather than reading a table. Get the rate from a K-factor: degree days accumulated divided by gallons used between two stick readings. Houses differ by a factor of three, so a K-factor beats any general figure — see how long will heating oil last.

Degree days per gallon. Fuel dealers compute one for every automatic-delivery customer and use it to decide when to send a truck. It encodes your house's insulation, your burner's efficiency and your habits in a single number that is roughly stable through a season.

About 138,500 Btu per gallon for the 15–500 ppm sulfur distillate grade and 91,452 Btu per gallon for propane, per EIA's thermal conversion factors. Distillate spans roughly ±0.5 % across the sulfur grades, so treat the oil figure as a band rather than a constant.

On days of supply, not on a fraction of tank. A quarter tank is twelve inches on a 275 in October and twelve inches in January, but those are six weeks and eight days respectively. Compute the days and compare against your supplier's cold-weather lead time, not the one they quote in autumn.

Because liquid propane expands about six times as much as water for the same temperature rise, and the vapour space absorbs it. NFPA 58 sets the filling limit, so a 500-gallon vessel holds about 400 gallons of propane.

Effectively yes. Propane must vaporise to feed appliances, and the rate depends on the wetted surface inside the tank and the outside temperature. A small tank at a low level on a very cold day can fail to meet peak demand while still holding liquid.

Water-finding paste on the bottom few inches of a clean stick, lowered to the tank floor and held for thirty seconds. The paste changes colour up to the water line. An inch of water is about 1.8 gallons in a 275 vertical and 6.2 gallons in a 275 horizontal.

In an aboveground tank a trace to a quarter inch is normal condensation; more than an inch should be pumped. In a regulated underground tank, an unexplained presence of water is an unusual operating condition reportable to the implementing agency within 24 hours under 40 CFR § 280.50.

It breeds microbial growth at the oil–water interface, corrodes steel from the inside where you cannot see it, can ice a fuel line in a deep freeze, and it inflates your readings — your stick measures total depth, not fuel depth.

Almost always a jammed disc or a gummed float hinge. Loosen the sight-glass cap and press the disc down gently; if it springs back to a different level it was stuck and the new level is roughly right. If it does not move at all, treat the gauge as dead and stick the tank.

Rule out the ordinary causes first: a water bottom counted as fuel, thermal contraction after a warm delivery, and a misread chart for the wrong orientation. If none of those account for it, get a professional tightness test. On a regulated UST a sudden loss of product is reportable within 24 hours.

Almost certainly not. 40 CFR § 280.12 excludes any tank storing heating oil for consumptive use on the premises where it is stored, and that exclusion has no gallon limit — the 1,100-gallon figure people quote is a separate entry covering farm and residential motor fuel tanks. Several states regulate residential heating-oil tanks under their own programmes, so check locally.

It depends on water capacity and on which code your jurisdiction enforces. OSHA's 29 CFR § 1910.110 Table H-23 requires 10 ft for containers up to 500 gallons and 25 ft for 501–2,000 gallons, reducible to 10 ft for a single container of 1,200 gallons or less at least 25 ft from any other LP-gas container over 125 gallons. Most states adopt NFPA 58, whose table differs for small containers.

Under 40 CFR § 112.8(c)(2), enough for the entire capacity of the largest single container plus sufficient freeboard to contain precipitation. The widely used 110 % figure is a design convention layered on top of that floor, not the regulatory text.

It supports it; it does not satisfy it alone. 40 CFR § 280.43(a) also requires daily recorded measurements, reconciliation against delivery receipts, metered dispensing, and monthly measurement of any water level to the nearest one-eighth of an inch.

A capacity table produced by physically measuring the tank rather than computing from nominal dimensions, under ISO 7507-1 or the equivalent API MPMS chapters, with corrections for plate thickness, shell expansion and tilt. You need one for custody transfer or any figure that has to survive a dispute.

Observed volume is what you gauged, at whatever temperature it was. Gross standard volume is that corrected to a 60 °F reference under API MPMS Ch. 11.1 with ASTM D1250 or ISO 91. Net standard volume is gross with sediment and water deducted. A traded barrel is a net standard barrel.