Calculate the volume of boxes, cylinders, cones, spheres, tanks, and other 3D shapes with instant formulas, cubic feet, liters, and gallon conversions.
Enter values and click calculate to see the volume
Sphere Formula:
V = (4/3) × pi × r^3
You can use this calculator for quick geometry homework, tank sizing, shipping estimates, and fill-material planning. The process is simple, but accuracy depends on choosing the right shape and entering your dimensions in one unit system.
Pick the 3D solid that most closely matches your object. Use a rectangular prism for a box, a cylinder for a tank or pipe, and a sphere for round objects. If your item is not perfect, choose the closest simple shape and treat the result as an estimate.
Keep every input in the same measurement unit. If one dimension is in inches and another is in feet, convert them before you calculate. Mixed units are one of the most common reasons a manual answer and a calculator answer do not match.
The calculator shows the matching formula for the selected shape. This makes it easier to check your work, understand where the result comes from, and learn how to calculate volume manually when you need to show steps in class or at work.
A raw result in cubic units is often only the first step. If you are working with liquid capacity, you may need gallons or liters. If you are ordering fill material, you may need cubic yards or cubic meters.
Start by deciding whether you care about the outside size of an object or the inside space it can hold. That choice matters. For a fish tank, rain barrel, or fuel container, you want the inside dimensions because you are measuring capacity. For a block of wood or a storage crate, you may care about total occupied space instead. A simple measurement error at the start can push the final answer far off target, especially for shapes that use radius in a squared or cubed term.
You should also know that the best shape is not always obvious. A pill bottle may be close to a cylinder, a capsule, or a tube depending on what part you are measuring. A domed tank may be modeled as a cylinder plus two smaller rounded sections. If your object is irregular, this calculator still helps because it gives you a strong baseline estimate. In practical work, that is usually more useful than guessing.
A volume result is more useful when you understand the unit, the shape assumptions, and what the number means in a real project.
Volume is measured in cubic units because it describes three-dimensional space. If you enter feet, your answer is in cubic feet. If you enter inches, your answer is in cubic inches. This is different from area, which uses square units and only describes a flat surface.
Capacity is usually the usable inside volume of a container. A tank with 12 cubic feet of inside space holds about 89.8 US gallons because 12 × 7.48052 = 89.76624. That is why conversions matter for aquariums, barrels, totes, and process tanks.
A small change in radius can create a large change in total volume. That is especially true for a sphere or cylinder, where the radius is squared or cubed. Accurate measurements usually matter more than adding extra decimals.
You should treat the result as a measurement of space, not as a final purchasing order, until you adjust it for your real use case. For example, if you are estimating gravel or topsoil, you may want to round up slightly because material settles. If you are estimating liquid storage, you may want to round down because many tanks need free space at the top for safety, expansion, or sloshing.
Another important point is shape fit. A rectangular prism is a strong model for a shipping box or raised bed, but it overstates capacity when the walls are thick or the corners are rounded. A cylinder is great for pipes, silos, and drums, but a tank with a dome or sloped base will not hold exactly the same amount as a simple straight cylinder with the same outside dimensions. In those cases, use the calculator for a solid baseline and adjust with field data if you need a final engineering value.
If your answer seems too high, check that you did not enter diameter in a radius field. If your answer seems too low, confirm that you used the full inside height and not the outside shell height. Those two issues explain a large share of bad results on volume pages.
If you want to calculate volume manually, the key is to match the correct formula to the correct solid and keep every dimension in the same unit.
Imagine you need the capacity of a cylindrical water tank with an inside diameter of 4 feet and a straight height of 8 feet. The cylinder formula uses radius, so divide the diameter by 2 first. That gives you a radius of 2 feet.
Now apply the formula for a cylinder: V = pi × r^2 × h. Substitute the values: V = 3.14159 × 2^2 × 8. Square the radius first: 2^2 = 4. Then multiply: 3.14159 × 4 × 8 = 100.53088. Rounded to two decimals, the tank volume is 100.53 cubic feet.
If you need gallons, multiply cubic feet by 7.48052. That gives 100.53088 × 7.48052 = 751.99 US gallons. If you need liters, multiply cubic feet by 28.3168. The same tank holds about 2,846 liters.
This is why a good volume calculator saves time. It handles the math quickly, but it also helps you move from pure geometry into practical planning. You can use the same method for a fuel tank, a rain barrel, a storage drum, or a process vessel. The shape formula gives you the base answer, and the unit conversion turns that answer into something you can order, compare, or communicate to a customer.
You rarely calculate volume just for the number itself. Most of the time, you need it to make a practical decision about storage, materials, shipping, or fit.
A bed that measures 8 ft long, 4 ft wide, and 1 ft deep has a rectangular prism volume of 32 cubic feet. Divide by 27 and you need about 1.19 cubic yards of soil before allowing for settling. That is much more reliable than ordering by guess.
A footing that measures 20 ft by 1.5 ft by 0.5 ft has a volume of 15 cubic feet. That equals about 0.56 cubic yards. This is a useful estimate before you call a supplier or compare bag counts for a small pour.
A tank with inside dimensions of 36 in × 18 in × 16 in holds 10,368 cubic inches. Multiply by 0.004329 and the capacity is about 44.9 US gallons. In practice, usable capacity will be slightly lower because you do not fill right to the top.
A box that is 18 in × 12 in × 10 in has a volume of 2,160 cubic inches. Divide by 1,728 and you get 1.25 cubic feet. This helps with warehouse slot planning, freight estimates, and comparing product packaging sizes.
A cylinder with a 1.25 ft radius and a 3 ft height has a volume of about 14.73 cubic feet. Multiply by 7.48052 and the barrel holds about 110.2 US gallons if it is filled to the top.
For a tube with outer radius 6 in, inner radius 5 in, and length 48 in, use the tube formula. The result is pi × 48 × (36 - 25), which is about 1,658.76 cubic inches of material in the wall around the hollow center.
These examples show why the same calculator works across many fields. Landscapers often need cubic yards. Lab work and food prep often use liters or milliliters. Construction planning often uses cubic feet or cubic meters. Shipping teams may stay in cubic inches because those units line up with carton dimensions and carrier pricing rules.
A useful rule of thumb is to round up for fill material and round down for liquid storage unless you know the container is designed to run full. That habit reduces waste in one case and prevents overflow in the other.
The biggest gap on many volume pages is practical conversion guidance. People often know the raw volume but still need a unit that fits the real job.
Use cubic feet for jobsite planning, bins, sheds, and shipping boxes. Use gallons for water tanks, aquariums, pools, and fuel containers in the United States. Use liters and milliliters in science, healthcare, and kitchen or lab settings.
If a product spec is in metric units but a local supplier quotes in US customary units, finish the shape formula first and convert only once at the end. That keeps your math cleaner and reduces rounding error.
Suppose a rectangular tank measures 5 ft long, 2 ft wide, and 2.5 ft high. First calculate the rectangular prism volume: 5 × 2 × 2.5 = 25 cubic feet. Then convert cubic feet into gallons: 25 × 7.48052 = 187.013 US gallons.
If you want liters instead, multiply gallons by 3.78541 or convert directly from cubic feet. The same 25 cubic feet equals about 707.92 liters. Both answers describe the same amount of space. They simply fit different industries and buying habits.
This matters any time you compare US and metric product listings. One supplier may sell a tote by liters while another sells a similar tank by gallons. With a correct unit conversion, you can compare them fairly, avoid overbuying, and communicate the same capacity to every person on your team.
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These questions target the same topics users often search in Google before they trust a volume result.
You can enter all dimensions in the same unit and read the answer as cubic units of that measure. For planning and storage, you can then convert that result into liters or US gallons.
This calculator uses radius for spheres, cylinders, cones, capsules, and tubes. If you only know diameter, divide it by 2 before entering the value. Using diameter in a radius field makes the final volume far too large.
First calculate volume in cubic feet or cubic inches, then convert it. One cubic foot is about 7.48052 US gallons, and one cubic inch is about 0.004329 US gallons.
Yes. Use the cylinder option for round tanks, rectangular for box-shaped tanks, and tube for hollow spaces. The answer helps you estimate capacity for water, fuel, grain, and similar materials.
Volume is the amount of three-dimensional space an object occupies. Capacity usually means how much a container can hold inside. For most tanks and bottles, the values match when you measure the inside dimensions.
Most mismatches come from mixed units, entering diameter instead of radius, rounding pi too early, or placing a dimension in the wrong field. Keep every measurement in one unit and round only after the full calculation.
Yes. Once you know the space in cubic feet, cubic yards, or cubic meters, you can use that number to estimate fill materials such as concrete, mulch, gravel, sand, or topsoil.
For an irregular object, use the water displacement method. Measure the starting water level, submerge the object, and subtract the original volume from the new volume to find the displaced amount.
The rectangular prism formula is V = l × w × h, where l is length, w is width, and h is height. Multiply all three dimensions in the same unit to get cubic units.