Tank Volume Calculator
Find the volume of cylindrical tanks (vertical or horizontal) in barrels, gallons, and liters.
Published by Blueprint Dynamics. Planning tools, not professional advice. Read the formula, assumptions, and examples below before relying on a result. Independent professional review is not claimed. Learn more about our methodology →
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Static geometric/pressure illustrations only—not a well-control calculation, drilling program, equipment pressure rating or operating authorization. Qualified petroleum/safety personnel must validate depth definitions, fluid conditions, friction and margins.
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About the Tank Volume Calculator
Storage and process tanks are everywhere in oil and gas, from mud pits and frac tanks on the rig to production stock tanks and saltwater disposal vessels at the battery. Being able to convert a tank's physical dimensions into a reliable capacity is basic to inventory, custody transfer, spill planning, and treatment chemical dosing. This calculator sizes a cylindrical tank and reports its volume in cubic feet, US gallons, oilfield barrels, and liters at once.
Because tanks in the field are mounted both ways, the tool lets you pick a vertical or horizontal orientation and simply asks for the diameter and the height or length. For a full cylinder the geometry is the same either way, so you get a clean total capacity that you can then relate to gauge readings.
Reporting the answer in four units keeps everyone on the same page. Production reports run in barrels, chemical suppliers work in gallons, tank data plates are often in cubic feet, and international or lab contexts use liters, so the conversions are done for you.
How the Tank Volume Calculator works
The tool models the tank as a right circular cylinder. It first finds the radius as half the entered diameter, then computes volume in cubic feet as pi times the radius squared times the height (or length for a horizontal tank): V = π × r² × h. This is the exact geometric volume of a full cylinder.
From cubic feet it applies fixed conversions to the other three units. Gallons equal cubic feet multiplied by 7.48052, since a cubic foot holds that many US gallons. Barrels equal cubic feet divided by 5.615, because one 42-gallon oilfield barrel occupies 5.615 cubic feet. Liters equal the gallon figure multiplied by 3.78541.
Every output recalculates instantly when you change diameter, height, or orientation. Note that the result is the full, brim-full capacity of the cylinder; a partially filled tank holds proportionally less, and heads on a real horizontal vessel add a small amount beyond the plain cylinder.
Worked example
Take a vertical tank 12 ft in diameter and 20 ft tall, the default. The radius is 6 ft, so the volume is π × 6² × 20 = π × 36 × 20 = 2,262 cubic feet.
Converting, that is 2,262 × 7.48052 = about 16,921 US gallons, or 2,262 ÷ 5.615 = about 402.9 barrels, or roughly 64,046 liters. So a 12 by 20 ft stock tank holds about 403 bbl when full. If your daily production were 40 bbl, this tank would take roughly ten days to fill, which tells you how often it needs to be hauled or transferred.
Tips & common mistakes
- Remember the tool reports full capacity. To read a working volume, multiply by the fraction of height actually filled for a vertical tank, and use a proper strapping table for a partially filled horizontal tank.
- Real horizontal and vertical tanks have dished or coned heads that add volume beyond the plain cylinder. For custody-grade accuracy use the manufacturer's strapping table rather than a geometric estimate.
- Keep the oilfield barrel straight: it is 42 US gallons and 5.615 cubic feet, not the 55-gallon drum some crews picture. This tool uses the correct 5.615 factor.
- Use this capacity for secondary containment sizing. Regulations often require a berm or dike that holds at least the largest tank's volume plus a freeboard allowance, so start from the full-tank number.
- When dosing treatment chemicals by concentration, work from the actual liquid volume in the tank, not the tank's total capacity, or you will over- or under-treat the batch.
Tank Volume Calculator: frequently asked questions
Does orientation change the total volume?
For a full cylinder, no. A 12 ft by 20 ft cylinder holds the same total whether it stands vertical or lies horizontal. Orientation matters only when the tank is partially filled, because the relationship between liquid height and volume differs between the two, which is why gauging a horizontal tank needs a strapping table.
How many cubic feet are in an oilfield barrel?
One 42-gallon oilfield barrel equals 5.615 cubic feet. This calculator divides the cubic-foot volume by 5.615 to report barrels, so the numbers line up with standard production and custody-transfer reporting.
Why doesn't the barrel here equal 55 gallons?
A 55-gallon figure refers to a shipping drum, not the petroleum barrel. In oil and gas, one barrel is defined as 42 US gallons. The tool uses the petroleum barrel throughout, so its bbl output matches field and regulatory conventions.
How do I find a partial fill volume?
For a vertical tank, multiply the full capacity by the ratio of the filled height to the total height, since volume rises linearly with level. For a horizontal tank the relationship is not linear, so use the tank's calibrated strapping chart or a horizontal-cylinder partial-volume formula.
Does this account for tank heads?
No. It computes the volume of a plain right cylinder. Real tanks with dished, coned, or elliptical heads hold a bit more, so for inventory that must be exact, rely on the manufacturer's strapping table which measures the true internal shape.
Can I use it to size spill containment?
Yes, as a starting point. Take the full-capacity figure for your largest tank and add the required freeboard and any displaced volume from other equipment in the berm. Always confirm the exact percentage and freeboard your local regulations require before finalizing containment dimensions.