Cubic Feet Calculator

What Is a Cubic Foot?

A cubic foot is a unit of volume equal to the space inside a cube with sides one foot long. It is written as ft³ or cu ft. One cubic foot equals 1,728 cubic inches, 0.0283 cubic meters, 7.481 US gallons, or approximately 28.317 liters. Cubic feet are the standard volume measurement in the United States for rooms, storage spaces, shipping containers, appliances, and construction materials. Enter length, width, and height in the calculator above to find the volume in cubic feet and equivalent units instantly.

How to Calculate Cubic Feet?

For rectangular spaces, multiply length times width times height in feet: Volume = L x W x H. A room 12 feet long, 10 feet wide, and 8 feet high contains 960 cubic feet. If measurements are in inches, multiply them and divide by 1,728 (the number of cubic inches in a cubic foot). If in meters, multiply and then multiply the result by 35.315 to convert cubic meters to cubic feet. The calculator above accepts any unit and converts automatically.

How to Calculate Cubic Feet for Irregular Shapes?

For cylindrical objects (pipes, tanks, tree trunks): Volume = pi times radius² times height, then convert to cubic feet. A cylindrical tank 3 feet in diameter (1.5 foot radius) and 5 feet tall: V = pi times 2.25 times 5 = 35.34 cubic feet. For triangular prisms: V = (1/2 times base times height of triangle) times length. For irregular shapes, break them into rectangular and cylindrical components, calculate each separately, and add the results together.

Common Volumes in Cubic Feet

Standard shipping container (20-foot): approximately 1,170 cubic feet. Typical refrigerator: 18-25 cubic feet. Standard washing machine: 3-5 cubic feet (drum capacity). Walk-in closet (6x6x8): 288 cubic feet. Single car garage (12x20x8): 1,920 cubic feet. Two-car garage (20x24x9): 4,320 cubic feet. A standard moving box (medium, 18x18x16 inches): approximately 3 cubic feet. A cord of firewood measures 128 cubic feet (4x4x8 feet). These reference values help you estimate storage needs, shipping costs, and material requirements.

How to Convert Between Volume Units?

Common conversions from cubic feet: 1 ft³ = 7.481 US gallons. 1 ft³ = 28.317 liters. 1 ft³ = 0.0283 cubic meters. 1 ft³ = 1,728 cubic inches. 1 cubic yard = 27 cubic feet. 1 cubic meter = 35.315 cubic feet. For large volumes, cubic yards are more practical (gravel, concrete, and landscaping materials are often sold by the cubic yard). For international trade and science, cubic meters are standard. The calculator above provides all common conversions alongside the cubic foot result.

Cubic Feet in Shipping and Storage

Moving companies estimate costs based on cubic feet of belongings. A studio apartment contains roughly 150-300 cubic feet of furniture and boxes. A one-bedroom apartment averages 300-500 cubic feet. A three-bedroom house typically requires 800-1,200 cubic feet of truck space. Storage unit sizes are quoted in square feet but cubic feet determines actual capacity: a 5x10 unit with 8-foot ceilings provides 400 cubic feet. Freight shipping charges often use dimensional weight, which calculates cubic feet and converts to an equivalent weight, charging whichever is greater between actual weight and dimensional weight.

Cubic Feet for HVAC and Appliances

HVAC systems are sized based on room volume in cubic feet. Air conditioner BTU requirements correlate with room cubic footage, not just square footage. A room with high ceilings needs more cooling capacity than the same floor area with standard ceilings. Refrigerator capacity is measured in cubic feet (a family of four typically needs 18-22 cu ft). Washing machine capacity is also in cubic feet (3.5-5.5 cu ft for standard, 4.5-6.0 for large capacity). Microwave interior volume ranges from 0.5 to 2.2 cubic feet. Knowing the cubic footage of your space and appliances ensures you purchase equipment sized correctly for your needs.

CFM: Cubic Feet Per Minute

CFM measures airflow rate, crucial for ventilation design. A bathroom exhaust fan rated at 80 CFM moves 80 cubic feet of air every minute. To determine the required CFM for a room, divide the room volume by the desired air changes per hour, then divide by 60. A 1,200 cubic foot room needing 6 air changes per hour requires 1,200 times 6 divided by 60 = 120 CFM. Industrial ventilation, HVAC ductwork, and clean room design all depend on accurate CFM calculations derived from cubic foot volumes.

Frequently asked questions