Tank Volume Calculator

Q: What is the difference between diameter and radius?

The diameter is the full distance across a circle from one side to the other. The radius is half of that, from the center to the edge. This calculator uses diameter, so you do not need to divide by two. Just measure straight across the widest part of your round tank.

Q: What is the difference between US gallons and imperial gallons?

A US gallon is 3.785 liters. An imperial gallon is 4.546 liters. Imperial gallons are about 20% larger. The US gallon is used in the United States, while the imperial gallon is used in the United Kingdom and some other countries. Make sure you pick the right one for your region.

Q: Do the leg height measurements affect the volume?

No. Leg height is the height of the support legs under the tank. It does not change the volume inside the tank. The calculator includes it so you can record the full tank setup, but it is not used in the volume formula.

Q: What is a 2:1 elliptical head tank?

A 2:1 elliptical head is a common end cap shape on pressure vessels and industrial tanks. The depth of the curve is one quarter of the tank diameter. This calculator models the two elliptical ends plus the straight cylinder section in between to give you the total volume.

Q: Can I use this calculator for a propane tank?

Yes. Most propane tanks are horizontal cylinders or horizontal capsules (cylinders with rounded ends). Select the shape that matches your tank, enter the dimensions, and the calculator will give you the volume. Keep in mind that propane tanks are typically filled to only about 80% capacity for safety.

Q: How do I calculate the volume of a tank that is not completely round or perfectly shaped?

Pick the shape in the calculator that is the closest match to your tank. If your tank has a combination of shapes, like a cylinder body with a cone bottom, use the Cone Bottom Tank option. For truly irregular shapes that do not match any option, you may need to break the tank into sections and add the volumes together.

Tank Volume Calculator

Updated May 23, 2026 By Jehan Wadia

Introduction

This tank volume calculator helps you find how much liquid a tank can hold. Pick your tank shape, enter the dimensions, and get the volume in gallons, liters, cubic feet, or other units. It works for round tanks, rectangular tanks, capsule tanks, cone bottom tanks, silos, and more. You can also adjust the fill level to see how much liquid is in a partially filled tank. If you already know the volume you need, switch to reverse mode to find the right tank size. Whether you need to measure a water tank, fuel tank, or storage tank, this tool gives you fast and accurate results.

How to Use Our Tank Volume Calculator

Enter your tank's shape and measurements to find out how much liquid it can hold. The calculator gives you the total volume, fill volume, and empty space in multiple units.

Select Tank Shape: Pick the shape that matches your tank. Options include horizontal cylinder, vertical cylinder, rectangle, capsule, oval, cone bottom, silo, and more.

Calculation Direction: Choose "Volume from Dimensions" to find volume using your tank's measurements. Choose "Dimension from Volume" to find a missing measurement when you know the volume you need.

Length Unit: Pick the unit your measurements are in, such as inches, feet, yards, centimeters, or meters.

Volume Unit: Pick the unit you want your results in, such as US gallons, liters, cubic feet, cubic meters, barrels, or imperial gallons.

Dimensions: Type in each measurement for your tank. The fields change based on the shape you picked. For example, a cylinder needs length and diameter, while a rectangle needs length, width, and height.

Fill Level (%): Use the slider or type a number from 0 to 100 to see how much volume your tank holds at a partial fill. Set it to 100% for full capacity.

Target Volume: This field shows up only in reverse mode. Enter the volume you want, and the calculator will solve for the missing dimension.

Dimension to Solve For: In reverse mode, pick which measurement you want the calculator to figure out for you.

Calculate Button: Press this to run the calculation and see your results, including volume in all units, tank details, and a fill level chart.

Reset Button: Press this to clear all inputs and start over with default settings.

What Is Tank Volume?

Tank volume is the amount of space inside a tank that can hold liquid or gas. Knowing your tank's volume helps you figure out how much water, fuel, oil, or other fluid it can store. Volume is measured in units like gallons, liters, or cubic feet. For general volume calculations across different geometric shapes, you can also use our volume calculator.

Why Calculate Tank Volume?

You need to know your tank's volume for many reasons. Farmers use it to manage water and chemical storage. Homeowners check heating oil tanks to know when to refill. Businesses track fuel tanks to plan deliveries. Knowing the exact volume prevents overfilling, saves money, and keeps things safe.

How Tank Volume Works

Every tank shape uses a different math formula. A rectangular tank is simple: multiply length times width times height. A cylinder volume calculator uses the radius and height with pi (π). Odd shapes like capsules, cones, or tanks with domed tops combine two or more formulas together. For cone-shaped sections, you can check the math with a cone volume calculator, and for spherical ends, a sphere volume calculator can help. The shape of your tank matters a lot because it changes the answer.

Partial Fill Volume

Tanks are not always full. A partial fill calculation tells you how much liquid is in the tank right now based on the fill level. This is especially useful for horizontal cylinders, where the volume does not go up evenly as the liquid rises. A tank that looks half full may not hold exactly half its total volume. Understanding the area of the circular cross-section is key to how partial fill formulas work for cylindrical tanks.

Common Tank Shapes

Horizontal Cylinder – Lies on its side. Common for fuel and propane tanks.
Vertical Cylinder – Stands upright. Used for water storage and breweries.
Rectangle – Box-shaped. Found in aquariums and industrial containers.
Capsule – A cylinder with rounded ends. Used in pressure vessels.
Cone Bottom – A cylinder with a cone at the bottom. Used in grain and chemical storage so contents drain fully.
Silo – A tall cylinder with a dome top. Used on farms for grain and feed.

Units of Measurement

Tank dimensions can be entered in inches, feet, yards, centimeters, or meters. Volume results can be shown in US gallons, liters, cubic feet, cubic meters, barrels, or imperial gallons. Picking the right units helps you match your tank specs or supplier requirements. If you need to convert between cubic measurements, our cubic feet calculator and cubic yard calculator can help. For projects involving pipes or plumbing connected to your tank, a pipe volume calculator is also useful. And if you're sizing a swimming pool or pond, check out our pool volume calculator for a tool tailored to those shapes.

Frequently asked questions

How do I measure my tank to get the right dimensions?

Use a tape measure on the outside of your tank. Measure the diameter across the widest part of a round tank, not the radius. For a rectangular tank, measure length, width, and height from the outside walls. If your tank has thick walls, subtract the wall thickness from each measurement to get the inside dimensions. Inside dimensions give you the most accurate volume.

What is the difference between diameter and radius?

The diameter is the full distance across a circle from one side to the other. The radius is half of that, from the center to the edge. This calculator uses diameter, so you do not need to divide by two. Just measure straight across the widest part of your round tank.

How does the reverse mode work?

Reverse mode finds a missing tank dimension when you already know the volume you want. Switch to Dimension from Volume, enter your target volume, fill in the dimensions you know, and pick the dimension to solve for. The calculator works backward to find the missing measurement for you.

Why does a horizontal cylinder not fill evenly?

When a cylinder lies on its side, the cross-section is a circle. At low fill levels, the liquid covers a narrow part of the circle, so volume rises slowly. Near the middle, the circle is widest, so volume rises faster. This means a tank that looks 50% full by height may not hold exactly 50% of the total volume.

What is the difference between US gallons and imperial gallons?

A US gallon is 3.785 liters. An imperial gallon is 4.546 liters. Imperial gallons are about 20% larger. The US gallon is used in the United States, while the imperial gallon is used in the United Kingdom and some other countries. Make sure you pick the right one for your region.

Do the leg height measurements affect the volume?

No. Leg height is the height of the support legs under the tank. It does not change the volume inside the tank. The calculator includes it so you can record the full tank setup, but it is not used in the volume formula.

How accurate is this tank volume calculator?

The calculator uses standard math formulas for each shape and is accurate for ideal geometric tanks. Real tanks may have slight differences due to wall thickness, welds, fittings, or dents. For the best results, use inside dimensions and keep in mind that the actual usable volume may be slightly less than the calculated volume.

What is a 2:1 elliptical head tank?

A 2:1 elliptical head is a common end cap shape on pressure vessels and industrial tanks. The depth of the curve is one quarter of the tank diameter. This calculator models the two elliptical ends plus the straight cylinder section in between to give you the total volume.

Can I use this calculator for a propane tank?

Yes. Most propane tanks are horizontal cylinders or horizontal capsules (cylinders with rounded ends). Select the shape that matches your tank, enter the dimensions, and the calculator will give you the volume. Keep in mind that propane tanks are typically filled to only about 80% capacity for safety.

How do I calculate the volume of a tank that is not completely round or perfectly shaped?

Pick the shape in the calculator that is the closest match to your tank. If your tank has a combination of shapes, like a cylinder body with a cone bottom, use the Cone Bottom Tank option. For truly irregular shapes that do not match any option, you may need to break the tank into sections and add the volumes together.

What does the fill level chart show?

The fill level chart shows how the volume inside your tank changes as the fill level goes from 0% to 100%. It helps you see that the relationship between fill height and volume is not always a straight line, especially for horizontal cylinders. You can use it to quickly estimate volume at any fill level.

How do I find out how many gallons are left in my tank?

Measure the height of the liquid inside the tank. Divide that height by the total inside height (or diameter for a horizontal tank) and multiply by 100 to get the fill percentage. Enter that percentage in the Fill Level field, and the calculator will show you how many gallons are in the tank.

What is a barrel as a volume unit?

In this calculator, a barrel refers to a US oil barrel, which equals 42 US gallons or about 159 liters. This unit is standard in the oil and petroleum industry. It is different from other barrel sizes used for beer or dry goods.

Can I calculate the weight of the liquid in my tank?

This calculator gives you the volume only. To find the weight, multiply the volume by the liquid's density. For example, water weighs about 8.34 pounds per US gallon or 1 kilogram per liter. Diesel fuel weighs about 7.1 pounds per gallon. Use the volume result from the calculator and multiply it by the density of your specific liquid.

What is the dish depth on a dish end tank?

The dish depth is how far the curved end cap sticks out from the flat face of the cylinder. It is the distance from the edge of the cylinder to the deepest point of the dish. Measure it from the end of the straight cylinder section to the tip of the curved end.