Every Tank Has a Capacity. Know It Before You Fill It.
Tank Calculator exists for one question — how much does this tank actually hold? — answered with published geometry, handbook head factors, honest liquid densities, and planning advice that treats every gallon as something a crew may have to pump, truck, or account for.
10
Tank shapes, cylinder to capsule
6
Input units, inches to metres
4
Head types for horizontal tanks
7
Output volume units
0
Accounts, uploads, or paywalls
Why this site exists
Tanks are the vessels everyone underestimates until they are on the truck — or overflowing in the yard. A 275-gallon heating-oil tote weighs more than a ton when full, and nobody would load a ton of anything on a guess. Yet tank capacity gets guessed at constantly, because the numbers that govern every decision — freight, pads, pumps, inventory, and the order itself — hide behind geometry that resists mental arithmetic. A horizontal cylinder fills along a curve, not a straight line. Dished ends hold volume flat-ended formulas ignore. And the liquid inside changes the weight by 40% between gasoline and water at identical volume.
Most answers online do not help. Supplier pages bury a simple question under catalog marketing. Forum threads recite πr²h without saying what happens below the half-way mark or at the heads. The cost of guessing wrong is not abstract: an overweight tanker gets turned away at the scale, a pad sized by eye creeps under its load, an overfilled tank finds the overflow it was never given, and a stick reading nobody can convert means a delivery dispute with no referee. Capacity is the first number every tank decision consumes — transport, structure, inventory, and price all size themselves from it — and it was the number the internet was worst at producing honestly.
We built TankCalculator.net to be the boring, correct alternative: one free tool, published formulas — area × length, integrated along the fill curve — and every assumption in plain sight. The head factors come from pressure-vessel handbooks, the liquid densities from the values the trade itself quotes, and the dip chart is generated from the same engine as the main answer. The calculator is the product; this page is the contract: how the engine works, what it does and does not promise, and the standards the guides around it are held to.
Every vessel on that pad has a capacity someone had to plan forPhoto: UnsplashHow the calculation actually works
Every input takes the same five stops. Because the chain is fixed and public, two different answers from this tool are mathematically impossible.
Your Dimensions
A shape from the dropdown and the dimensions that define it — length, diameter, width, height. Type what you actually measured; the engine only asks for the fields your shape uses.
Cross-Section Geometry
A circle, a rectangle, a stadium, an ellipse — the cross-section is computed exactly, so a horizontal cylinder is a true circle and an oval tank is a true stadium, not an approximation.
Volume
Cross-sectional area × length gives total capacity in cubic inches. A fill level turns it into filled volume through the circular-segment formula, with ullage (air space) reported alongside.
Heads & Corrections
Dish ends (hemispherical, 2:1 elliptical, torispherical) add their real volume to a horizontal tank, and an installation tilt is integrated along the axis so a leaning tank still reads true.
Weights & Dip Chart
The liquid's specific gravity converts volume to weight at full and current level, and the dip chart generator tabulates depth → volume → percentage → ullage at whatever step you choose.
10 Tank Shapes, One Dropdown
- Horizontal and vertical cylinders, rectangles, ovals, capsules, and ellipses
- Each shape only shows the dimensions it actually needs — no dead input fields
- Length basis switch for capsule tanks: straight (tan-tan) or overall end-to-end
Dish Ends & Head Types
- Flat, hemispherical, 2:1 elliptical, and torispherical (ASME F&D) heads
- Head volume and body (straight-side) volume reported separately, then totaled
- Dish depth auto-fills from the handbook factor — or type your own measurement
Dip Chart Generator
- Fixed steps (every 1 in / 1 cm / 5 in…) or percentage-of-depth steps (5%, 10%…)
- Each row shows depth, filled volume, percentage, and remaining ullage
- Readable in inches or centimetres, with CSV download and a print-ready layout
Liquid Weights & Units
- Presets for water, diesel, gasoline, milk, crude oil and more — plus custom density
- Results in U.S. gallons, imperial gallons, liters, cubic feet and metres, oil barrels
- Full and current-level weights in pounds, kilograms, and metric tons
Five audiences, one number
The same arithmetic serves a first-time DIYer and an engineer checking nozzle loads — they just read different parts of the result. These are the people we design for.
Tank Farm & Terminal Operators
A gauge reading is only as useful as the table behind it. Generate a dip chart for each vessel, laminate it, and hand it to the person on the catwalk — every stick reading becomes a volume, a percentage, and an ullage figure without a laptop in the rain.
Fleet & Transport Managers
A 275-gallon heating-oil tote weighs more than a ton when full. The weight converter turns any fill level into pounds and kilograms, so payload limits, axle weights, and pickup-bed loads are decided with numbers instead of "it felt about full."
Process & Mechanical Engineers
Horizontal vessels have dished heads, and heads hold volume. The head-type selection separates body volume from head volume, and the tilt correction handles vessels installed with a slope for drainage — the two details flat-ended calculators quietly ignore.
Agriculture & Rural Operations
Fuel tanks, milk vats, water tanks, fertilizer totes — rural storage is a fleet of different shapes. One tool covers the cylinder, the oval, the capsule, and the rectangle, and converts every answer to the gallons or liters your supplier quotes in.
DIYers & Students
A rain barrel, an aquarium stand, a homework problem about a partly filled cylinder — every one starts with "how much does this actually hold?" The calculator answers in seconds and shows the formula it used, so the number comes with the reasoning attached.
From a rain barrel to a tank farm — same math, different stakesPhoto: UnsplashSix decisions a capacity figure feeds
Capacity is never the deliverable — the payload plan, the pad, the dip table, and the order are. These are the decisions the tool is built to feed.
Transport & Payload
A fully loaded 500-gallon water tank is over two tons before the trailer weighs anything. Whether that means one trip or three is a payload decision, and payload decisions made from guesses end at the scale house.
Pads, Foundations & Structure
A vertical tank's filled weight is the load its pad, legs, and roof structure must carry — water alone runs 8.34 lb per gallon, and denser liquids run higher. Sizing the foundation starts with an honest capacity figure.
Ullage & Fill Planning
Thermal expansion, splash, and agitation all need headroom. The ullage column in the results and dip chart tells you exactly how much space remains at any level — the difference between a full tank and an overflowing one.
Inventory & Reconciliation
A stick reading of 34 inches means nothing on its own. A dip chart turns every depth into volume, so deliveries match invoices and shrinkage shows up the week it happens, not at year-end inventory.
Cost & Procurement
Fuel, milk, and chemicals are bought by the gallon or the litre. Converting tank geometry into capacity — and capacity into current contents — turns ordering from a calendar guess into a measured decision.
Mixing, Batching & Dosing
A batch recipe that calls for 40% of a tank needs the percentage to mean the same volume every time. The dip chart's percentage steps make "half full" a number the operator can hit with a gauge stick.
The mental-math anchors the engine refines
Four shortcuts cover most hallway estimates. The calculator keeps them honest by replacing each assumption with exact geometry and exact density.
V = π r² L
total capacity, horizontal/vertical cylinder
Radius r and length L in the same units. A 27" diameter × 60" tank holds π × 13.5² × 60 ≈ 34,350 in³ — about 148.7 US gallons. The calculator confirms it to the decimal.
A = r² cos⁻¹((r−d)/r) − (r−d)√(2rd−d²)
circular segment, partial fill
The area of a circle below depth d — the formula behind every partial-fill answer and every dip chart row. At quarter depth a cylinder holds far less than a quarter of its volume.
1 US gal = 231 in³
the conversion behind every gallon
Every cubic-inch result on the site flows through this constant (and its imperial and metric siblings). Water in a 148.7-gallon tank: 148.7 × 8.34 ≈ 1,240 lb of contents.
Water ≈ 8.34 lb/gal
SG 1.0 reference liquid
Diesel runs about 6.8–7.1 lb/gal (SG ≈ 0.84), gasoline about 6.0–6.2. Multiply the preset's specific gravity by the volume and the weight falls out — the calculator does it per fill level.
Payloads, pads, and ullage — all decided by the capacity figurePhoto: UnsplashWhat we promise — and what we don't
A capacity calculator earns trust by being precise about its own limits. Here is the complete list of both.
Published formulas only
Every result traces back to standard geometry: circular segments for partial fills, spherical caps and handbook factors for dish ends, Simpson integration for tilt. You can verify any answer by hand.
Honest liquid densities
The liquid presets use accepted specific gravities — water 1.00, diesel ≈ 0.84, gasoline ≈ 0.74, milk ≈ 1.03 — and a custom density field overrides any of them in lb/gal or kg/m³.
Capacity vs. working capacity, stated plainly
Geometric capacity is the number the formula gives; real vessels lose volume to internals, fittings, temperature, and the safe fill level your operator uses. We flag this instead of pretending precision.
Head factors from the handbook
Dish end volumes use the factors pressure-vessel handbooks publish — (2/3)πr³ per hemispherical head, πr³/3 per 2:1 elliptical head, ≈0.0809 D³ per ASME F&D head — not fitted guesses.
Estimates, not calibration certificates
Results are for planning and education. For custody transfer, regulatory reporting, or certified capacities, the vessel's calibration chart and a qualified engineer win — every time.
How the site itself is engineered
The calculation engine is half the story. The other half is the choices behind the page you are reading — why there is no account, no upload, and no premium tier.
Privacy by architecture
The entire engine is client-side JavaScript. Your tank dimensions, fill levels, and densities are processed in your own browser tab and never transmitted to our servers — not as a policy promise, but as a structural fact. There is no account system, no upload step, and no history stored anywhere on our side.
Instant by design
No spinners, no round trips. Results, the SVG diagram, and the dip chart update on every keystroke because the computation is a few multiplications running on your device. The site is statically built and served from the edge, so the tool is typically interactive in well under two seconds on a normal connection.
Free, ad-supported, and labeled
Every feature on the site is free with no usage caps. Advertising — clearly separated from calculator output and editorial content — pays the hosting bill. There is no premium tier hiding the useful half of the tool, and no email gate in front of a result.
Independent on purpose
We sell no tanks, take no affiliate commissions, and hold no manufacturer relationships. The liquid presets exist because they answer real questions, not because a supplier asked for them. When a vessel's calibration chart disagrees with our estimate, the chart wins and we say so on the page.
Runs in your browser — nothing to install, nothing sentPhoto: UnsplashHow the guides are written
The calculator is surrounded by guides — on the formulas behind each shape, the dish end and head geometry, and measuring and entering dimensions. Every one of them answers to the same five rules — and so do we, on this page.
- We show the working — guides walk through the formula, the units, and a worked example, so you can check our math rather than trust it.
- We label uncertainty — where a number depends on head geometry, temperature, or a safe fill allowance, we say so in the same breath as the number.
- We cite the standard, not vibes — head factors come from pressure-vessel handbooks, unit conversions from their defined values, and the mental-math anchors straight from the geometry.
- We update, and we date — content is reviewed against the current calculator behavior; if the tool changes, the guides change with it.
- We write for the trade and the first-timer — the same page serves an operator building a dip chart and a homeowner sizing a rain barrel, and neither gets talked down to.
Straight answers about the site
Tool-specific questions live in the homepage FAQ. These are the ones about us.
How accurate is the tank volume calculator?
What are dish ends, and why do they change the volume?
Why does a quarter-full tank hold less than a quarter of its volume?
Does the calculator account for a tilted tank?
Who is behind the site?
How is the site funded?
What are the quick rules of thumb for tank volume?
Can I use the results for regulatory or structural decisions?
Is the site really free?
Explore the site
Every homepage anchor and every page that explains, extends, and governs the tool.
Legal: Privacy · Terms · Disclaimer
Now size something
The calculator is free, instant, and runs entirely in your browser. Pick one of 10 tank shapes, choose your units, add dished heads or a tilt if the vessel has them — and get total capacity, filled volume, weights, and a printable dip chart in the time it took to read this page.
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