Linear Feet to Cubic Feet Calculator
Convert a straight run into cubic feet using length, width, height or thickness, quantity, void factor, waste, material density, and shape type for lumber, ducts, trenches, and channels.
▦Real-World Presets
Load a common lumber, duct, trench, or channel scenario, then adjust dimensions and factors to match your field measurements.
⚙Volume Inputs
Calculation Breakdown
▣Shape and Material Grid
📊Reference Tables
| Shape Type | Cross-Section Formula | Best For | Dimension Notes |
|---|---|---|---|
| Rectangular | width x height | Lumber, rectangular duct, box trench | Use actual width and thickness or inside duct dimensions. |
| Round | pi x (diameter / 2)^2 | Round duct, pipe void, bored hole | Width field is the diameter; height is ignored. |
| Half-round | 0.5 x pi x (diameter / 2)^2 | Gutters, half-pipe channels, scoops | Width field is the full outside or inside diameter. |
| Triangular | 0.5 x base x height | V trenches, wedges, triangular voids | Width is base; height is measured depth. |
| Trapezoid | ((top + bottom) / 2) x depth | Sloped trenches, swales, tapered channels | Width is top; secondary dimension is bottom width. |
| U-channel | wall x bottom + 2 x wall x side | Wood curbs, metal channels, formed rails | Secondary dimension is wall thickness, not bottom width. |
| Material / Basis | Typical Density | Common Use | Void Factor Guidance |
|---|---|---|---|
| SPF framing lumber | 28 lb/ft³ | Studs, blocking, framing runs | Use 0% unless measuring a hollow or notched section. |
| Western red cedar | 23 lb/ft³ | Exterior trim, light boards, channels | Use 0% for solid boards; add waste for defects. |
| Softwood plywood | 34 lb/ft³ | Ripped strips, sheet goods, panels | Use measured sheet thickness for strip volume. |
| Galvanized duct air | 0.075 lb/ft³ | Air volume in duct sections | Use inside dimensions and 0% void for air capacity. |
| Washed gravel | 100 lb/ft³ | Drain trenches, bedding, backfill | Use 25% to 40% when estimating solid stone volume. |
| Concrete fill | 145 lb/ft³ | Forms, channels, compacted pours | Use 0% for placed concrete volume, add waste for spillage. |
| Preset Scenario | Shape | Typical Dimensions | Planning Check |
|---|---|---|---|
| 2x4 stud bundle | Rectangular lumber | 1.5 in x 3.5 in x 8 ft | Good for total solid wood volume and stack weight. |
| Round duct run | Round cylinder | 6 in diameter x 30 ft | Use inside diameter for air volume calculations. |
| Rectangular duct | Rectangular air space | 8 in x 12 in x 24 ft | Counts contained air volume, not sheet metal volume. |
| Utility trench | Rectangular trench | 12 in x 18 in x 40 ft | Measure average depth after grading. |
| Trapezoid swale | Tapered channel | Top, bottom, and depth | Use several sections if the slope changes along the run. |
| Conversion | Formula | Example | Calculator Use |
|---|---|---|---|
| Linear feet to cubic feet | area in² x length ft / 144 | 96 in² x 10 ft = 6.67 ft³ | Main volume conversion. |
| Cubic feet to cubic yards | ft³ / 27 | 54 ft³ = 2 yd³ | Bulk fill and trench ordering check. |
| Cubic feet to cubic meters | ft³ x 0.0283168 | 35.31 ft³ = 1 m³ | Metric cross-check for all results. |
| Weight estimate | order ft³ x density | 10 ft³ x 34 = 340 lb | Useful for hauling, lifting, and storage checks. |
ℹVolume Tips
Converting linear feet to cubic feet involve determining volume, which is essential for calculating how much of a linear material you need for an specific project. The length of a material dont necessarily have a consistant width and height, and each material may have a changing cross-section. To calculate volume, you have to determine the area of the materials cross section and multiply that by the length.
If you use square inch for the area measurement, you will have to divide that value by 144 to convert it to cubic feet. The calculator allow you to enter the length of your material and also the width, diameter, height, and depth of the material. You can also select the shape of the material that you are measuring.
How to Convert Linear Feet to Cubic Feet
It is important to select the correct shape because different shapes has different formulas. For example, if you are measuring lumber or trenching, the cross section is most likely to be rectangular. However, if you are measuring the air volume in a pipe, for example, you will want to use the round shape setting on the calculator.
For measurements of ditches or swales, which can be sloped and have a different top and bottom width, you would use the trapezoid or triangle measurement setting. It is essential that you dont use the rectangular setting for a sloped ditch because this will make your measurements either too highly or low. To calculate the order volume of your material, the calculator will use the void factor and the waste percentage of the material.
The void factor calculate how much the amount of air in the material reduces the solid material. For framing lumber, for instance, which is a solid material, the void factor will be very close to zero. However, if you use topsoil or gravel, the void factor will be more higher because these materials contains air space between the particles of the material.
The void factor isnt the only measurement that will determine the weight and volume of the material that you order. You will also have to use the waste percentage. The waste percentage is used to account for any defects in the material.
For example, lumber may have knots or splits in it that cannot be use in your project. The waste percentage will account for this, and you will also have to enter it after you enter the void factor for the calculation. The calculator can give you the answer in cubic yards and meter.
It will also calculate the total weight of the material. Knowing the weight is important because you will want to know how heavy the load will be when you deliver the material to your project. The dimensions that you measure in the field may differ from what is on the drawing.
The length, quantity, and the void and waste percentages can all be adjusted once you have enter the dimensions of your material. Adjustments to the void and waste percentages will have a greater impact on the order volume than adjustments to the width. Therefore, you can use this calculator to test out different percentages of waste before you order your material.
To fully understand the calculator, you can refer to the reference tables at the bottom of the calculator. These table will tell you the densities of the materials. You can refer to them to ensure that your assumptions are the same throughout your project.
For example, if you are measuring the volume of a ditch, measure the width of the ditch at several different locations and use the average width. When measuring lumber, use the dressed dimensions of the lumber rather than the nominal dimensions. Although the two measurements may be very similar, the small difference between them will have a significant impact on the total volume and weight of the material that you order.
Using this calculator allow people to see how changes to the variables will change the final volume and weight of the material.
