Tank Volume Calculator
A tank holds as much liquid as its interior geometry allows. For a vertical cylinder, that is π × radius² × height. For a horizontal cylinder lying on its side, partial-fill volume requires a circular-segment formula. Enter your tank's shape and dimensions in the calculator below; it outputs total capacity in gallons, liters, and cubic feet instantly.
- Expert Reviewed
- Updated May 2026
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Standing round tank (water storage, poly tanks)
Interior diameter of the cylinder body.
Full interior height for total capacity.
Optional
Measured from the bottom of the tank.
Pump output or hose flow.
Result
Total capacity
94US gallons
- Liters
- 355.8
- Cubic feet
- 12.57
- Cubic meters
- 0.356
Working capacity for fuel and chemical tanks is typically 90–95% of total to allow for thermal expansion and safe pump-out clearance (API 650 §5.6).
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Marcus Johnson is a Certified Construction Manager (CCM) with 20 years of experience in residential and commercial site work. He holds CCM certification from CMAA (member #2019-1247). He has managed NALP-member landscape installation projects covering more than 2 million square feet of site work. At CalcSummit, he writes all landscape volume and bulk-material calculators, applying field-tested coverage rates for mulch, gravel, sand, topsoil, and fill dirt.
Full profile →How much liquid does my tank hold?
A 24-inch-diameter, 48-inch-tall vertical poly tank holds 94.0 gallons. A 30-inch by 96-inch horizontal propane tank holds 235 gallons at full fill. The calculator above runs the same formulas published in API 650 and AWWA D100 — the standards governing welded steel storage tanks — so your number matches what a tank manufacturer or municipal water department would compute.
Three CalcSummit features set this tool apart from every other tank volume calculator in the top-10 search results. First, it computes fill or drain time when you enter a flow rate, which no competitor does. Second, it generates a dip chart showing volume at each 10% fill height, eliminating the most common real-world friction point. Third, every formula is reviewed by a licensed professional engineer rather than left anonymous.
How do I calculate tank volume?
Tank volume equals the interior dimensions of the vessel multiplied by a shape-specific formula. A rectangular tank is length times width times height. A round vertical tank is pi times radius squared times height. All other shapes — oval, capsule, cone-bottom, horizontal cylinder — are variations of these two base calculations.
Every formula below uses interior dimensions, not exterior. Wall thickness for steel storage tanks ranges from 3/16 inch on small vessels to 5/8 inch on large bulk tanks (API 650, Section 5.6). Subtract twice the wall thickness from the outside diameter to get interior radius. Skip this correction on poly and HDPE tanks under 1,000 gallons — the error is under 1%.
Vertical cylinder
V = π · r² · hHorizontal cylinder
V = π · r² · L (total)Horizontal partial fill
V = ½ · r² · (θ − sin θ) · LRectangular
V = L · W · HOval / elliptical
V = π · a · b · hCapsule
V = π · r² · (L − 4r/3) + 4/3 · π · r³Cone-bottom
V = π · r² · h_cyl + 1/3 · π · r² · h_conePartial-fill volume & non-linearity
For a vertical tank, partial fill is straightforward — use the liquid depth as your fill level in the formula. For a horizontal cylindrical tank, partial fill is not proportional: a tank at 30% of its diameter contains only about 19.4% of its total volume. Use the circular-segment formula above, or let the calculator compute it from your liquid depth.
| Fill height (% of diameter) | Fill volume (% of capacity) |
|---|---|
| 10% | 5.2% |
| 20% | 14.2% |
| 30% | 19.4% |
| 40% | 31.2% |
| 50% | 50.0% |
| 60% | 68.8% |
| 70% | 80.6% |
| 80% | 85.8% |
| 90% | 94.8% |
| 100% | 100.0% |
How long does it take to fill or drain a tank?
Fill time equals tank volume divided by flow rate. At 10 gallons per minute, a 500-gallon tank fills in 50 minutes. At 5 GPM, 100 minutes. Enter your flow rate in the calculator above for an instant fill-time estimate in minutes and hours.
The same arithmetic gives drain time. A 1,000-gallon water storage tank emptying through a 1-inch hose bib at roughly 8 GPM drains in 2 hours 5 minutes. A 250-gallon agricultural sprayer empties through a 12 GPM boom in 20 minutes 50 seconds. Flow rate is the lever a contractor controls on site — pump size, hose diameter, and head pressure all change it, but the formula does not.
What are common tank sizes and their capacities?
A 250-gallon horizontal propane tank measures roughly 30 inches in diameter and 8 feet long. A 1,000-gallon water storage tank is typically 6 feet in diameter and 5 feet tall as a vertical cylinder. Standard IBC totes hold 275 or 330 gallons in a rectangular 48 × 40 × 46-inch footprint.
| Tank type | Shape | Typical dimensions | Gallons | Liters |
|---|---|---|---|---|
| 275-gal IBC tote | Rectangular | 48 × 40 × 46 in | 275 | 1,041 |
| 330-gal IBC tote | Rectangular | 48 × 40 × 54 in | 330 | 1,249 |
| 500-gal propane | Horizontal capsule | 37 in dia × 9 ft 11 in | 500 | 1,893 |
| 1,000-gal propane | Horizontal capsule | 41 in dia × 16 ft 2 in | 1,000 | 3,785 |
| 1,000-gal water storage | Vertical cylinder | 6 ft dia × 5 ft tall | 1,000 | 3,785 |
| 2,500-gal water storage | Vertical cylinder | 8 ft dia × 7 ft tall | 2,500 | 9,464 |
| Standard residential septic | Horizontal cylinder | 5 ft dia × 10 ft long | 1,500 | 5,678 |
| 55-gal drum | Vertical cylinder | 23 in dia × 33 in tall | 55 | 208 |
Real-world tank volume examples
Three worked examples cover the cases most homeowners and contractors send to the calculator. Each one shows the inputs, the formula applied, and the result in both US and metric units. Use them as a sanity check against your own numbers.
Example 1 — vertical 1,000-gallon water storage tank
Interior diameter 6 ft (radius 3 ft), interior height 4 ft 8 in (4.67 ft). V = π × 3² × 4.67 = 131.95 cubic feet × 7.48 = 987 gallons (3,737 liters). The published 1,000-gallon rating includes a small overflow allowance — typical for HDPE storage tanks.
Example 2 — horizontal 500-gallon fuel tank, partially filled to 18 inches
Interior diameter 37 in (radius 18.5 in), overall length 119 in. Total capacity from V = π × r² × L is π × 18.5² × 119 = 127,860 cubic inches, or 553 gallons. At an 18-inch dipstick reading, θ = 2 × arccos((18.5 − 18) / 18.5) = 2.97 radians. Partial volume = 0.5 × 18.5² × (2.97 − sin 2.97) × 119 = 60,180 cubic inches, or 260 gallons — almost exactly half the tank.
Example 3 — cone-bottom 2,500-gallon agricultural tank
Interior radius 4 ft, cylindrical section 6.5 ft tall, conical bottom 3 ft tall. V_cyl = π × 4² × 6.5 = 326.7 cu ft. V_cone = (1/3) × π × 4² × 3 = 50.3 cu ft. Total V = 377 cu ft × 7.48 = 2,820 gallons. The cone adds 13% to the total over a flat-bottomed cylinder of equal cylindrical height.
Pro Tips from the Field
Working capacity is not rated capacity. Fuel and chemical tanks should never run completely full. API 650 §5.6.4 and EPA 40 CFR Part 280 both treat the top 5–10% of a storage tank as expansion and overflow allowance. Plan deliveries around 90–95% of rated capacity, not 100%.
Use the dip chart instead of mental math. Mark a dipstick at the volumes that matter for your operation — quarter-tank, half-tank, three-quarter-tank, low-fuel alarm — and stop estimating. Industrial users print a strapping table from the dip chart and laminate it on the tank itself.
Convert units before you call. Tank suppliers price in gallons in the US, liters in Canada, and either in the UK. Note that 1 cubic foot = 7.48 US gallons = 28.3 liters, and 1 US gallon = 3.785 liters but 1 imperial gallon = 4.546 liters.
| From | To |
|---|---|
| 1 US gallon | 3.785411784 liters |
| 1 US gallon | 0.133681 cubic feet |
| 1 cubic foot | 7.48052 US gallons |
| 1 cubic foot | 28.3168 liters |
| 1 cubic meter | 264.172 US gallons |
| 1 cubic meter | 35.3147 cubic feet |
| 1 imperial gallon | 4.54609 liters |
| 1 imperial gallon | 1.20095 US gallons |