Fuel Tank Size Calculator

Calculator Inputs

Tank shape

Dimension unit

Result volume unit

Length or straight shell length

Width or oval major diameter

Height or oval minor diameter

Round tank diameter

Measured fuel depth

Used for horizontal round tanks. Enter 0 to use fill percent.

Fill level percent

Reserve percent

Expansion space percent

Fuel density kg/L

Fuel price per liter

Fuel economy value

Fuel economy type

Trip distance in kilometers

Formula Used

Rectangular tank: V = L × W × H.

Vertical or horizontal cylinder: V = π × r² × length.

Elliptical cylinder: V = π × a × b × length.

Capsule tank: V = π × r² × straight length + 4/3 × π × r³.

Safe maximum fill: capacity × (1 − expansion space percent ÷ 100).

Usable fuel: current fuel volume − reserve volume.

Fuel mass: fuel volume in liters × fuel density.

Range: usable fuel × kilometers per liter.

How to Use This Calculator

Select the tank shape that best matches your design.
Choose the unit used for your dimensions.
Enter only the dimensions required for your shape.
Set fill level, reserve, expansion space, and density.
Add fuel price and economy values when range is needed.
Press the calculate button to view the result above the form.
Download the result as a CSV or PDF report.

Example Data Table

Shape	Dimensions	Formula	Approximate Capacity
Rectangular	2 m × 1 m × 0.8 m	L × W × H	1,600 L
Vertical cylinder	1 m diameter, 1.2 m height	π × r² × H	942.478 L
Horizontal cylinder	0.9 m diameter, 2.4 m length	π × r² × L	1,526.814 L
Capsule	0.8 m diameter, 1.8 m straight length	Cylinder plus sphere	1,172.861 L

Fuel Tank Sizing Guide

Why Tank Volume Matters

A fuel tank is more than a container. It is part of a physical system. Its size affects range, weight, balance, cost, and safety. A small error can cause poor planning. It can also leave too little reserve. A larger tank adds mass. That mass may reduce performance. Good sizing keeps these limits visible.

Shape Controls Capacity

Tank shape is the first factor. Rectangular tanks use length, width, and height. Cylindrical tanks use radius and length. Elliptical tanks use two different diameters. Capsule tanks add the volume of two hemispherical ends. Each shape uses geometry. Unit conversion must happen before the formula is used. This calculator converts every entered length to meters first. It then converts the result to liters and other units.

Fill Level And Reserve

Usable fuel is not always equal to total volume. Tanks need space for expansion, foam, and movement. Operators often keep a reserve amount. The reserve protects the engine from air intake. It also gives time to reach service. Fill level shows what is actually inside the tank. Safe fill capacity can be lower than full geometric capacity. This is important in warm areas and moving vehicles.

Mass, Cost, And Range

Fuel has density. Density turns volume into mass. Gasoline, diesel, aviation fuel, and other liquids differ. This affects load and support design. Fuel price estimates the value of the current fill. Economy estimates travel range. The calculator supports common economy styles. It can show kilometers per liter, liters per 100 kilometers, or miles per gallon. These values help compare design choices.

Practical Use

Use realistic dimensions from drawings or measurements. Keep all units consistent. Add reserve rules used by your project. Check the result against standards for your application. Do not ignore mounting space, vents, baffles, fittings, and legal limits. The calculator gives an engineering estimate. Final tank design should still be checked by a qualified person when safety matters.

Reviewing outputs together avoids hidden mistakes. A tank may look large enough by volume, yet fail by usable range. Another tank may meet range needs, but exceed weight targets. Recheck inputs after each change. Small dimension changes can create large capacity differences in curved tanks.

FAQs

1. What does this fuel tank size calculator measure?

It estimates total capacity, safe fill volume, usable fuel, reserve, mass, cost, and travel range. It uses geometric formulas based on the selected tank shape and entered dimensions.

2. Which tank shapes are supported?

The calculator supports rectangular, vertical cylinder, horizontal cylinder, elliptical cylinder, and capsule tanks. These shapes cover many common vehicle, generator, storage, and fabrication layouts.

3. What is expansion space?

Expansion space is empty volume left inside the tank. It allows fuel to expand and move. It also helps reduce overflow risk during heat, vibration, or transport.

4. Why is reserve fuel subtracted?

Reserve fuel is kept aside for safety. It helps prevent air intake, unexpected shutdowns, or poor range planning. Usable fuel is the current fuel amount after reserve is removed.

5. Can I use inches or feet?

Yes. Select inches or feet from the dimension unit field. The calculator converts all dimensions to meters before applying the physics formulas.

6. What density should I enter?

Use the density of your fuel in kilograms per liter. Gasoline is often near 0.745 kg/L. Diesel is often higher. Check your fuel specification for better accuracy.

7. How is range calculated?

Range equals usable fuel multiplied by fuel economy. The calculator converts supported economy formats into kilometers per liter before estimating distance.

8. Is this suitable for final tank design?

It is useful for planning and early checks. Final tank design should also consider standards, materials, fittings, vents, baffles, mounting, testing, and professional review.