Cubic Feet Calculator
Calculate volume in cubic feet from length, width, and height.
Supports 11 length units, mixed ft/in and m/cm inputs, and 21 volume units.
Updated August 3, 2026
Introduction / overview
The Cubic Feet Calculator finds the volume of a box-shaped object or space in cubic feet from just three numbers: its length, width, and height. Type any two of them, and it works out the third — it doesn’t just multiply forward, it also solves the reverse direction for you.
If you have ever stood in a garden aisle wondering how many bags of soil your planter actually needs, or held up a box and guessed whether it would fit in the boot of your car, this tool settles it in seconds. Every dimension can be entered in the unit you have on the tape measure — inches, feet, yards, meters, centimeters, and more — and the answer comes out in cubic feet, or any volume unit you prefer.
The math is exact. One foot is defined as exactly 0.3048 meters, so every metric-to-imperial conversion here is based on fixed definitions rather than rounded shortcuts — your answer is as accurate as the numbers you measure.
Who is this for?
- Gardeners and DIYers figuring out how much soil, mulch, compost, or gravel a bed or planter needs.
- Movers and shippers checking whether a box fits in a van, a trunk, or a storage unit, and estimating shipping volume.
- Builders and hobbyists estimating concrete, sand, or air volume for a room, slab, or enclosure.
- Aquarium and water lovers converting a tank’s dimensions into gallons or liters.
Planning a larger garden project? Our Soil Calculator takes a volume like this and breaks it into bags versus bulk deliveries, with cost estimates, so you know exactly what to order.
How to use / quick start
- 1Enter the Length of the box or space. It starts in feet and inches — type the feet in the first slot and any extra inches in the second, or switch to meters, centimeters, inches, or another unit.
- 2Do the same for Width and Height. The volume in cubic feet appears the moment all three are filled in.
- 3To read the result in another unit, open the “More conversion options” section and pick one — cubic yards, gallons, liters, cubic meters, and more. Your original numbers stay untouched; only the view changes.
- 4Know the volume but not a dimension? Type the volume and the two dimensions you have — the calculator works out the missing one.
Example: a simple raised bed
You’re filling a planter that is 4 ft long, 2 ft wide, and 1 ft deep. Enter those three numbers:
The calculator shows 8 ft³. That’s roughly four 2-cubic-foot bags of soil, or about a third of a cubic yard.
Example: solving for a missing dimension
Suppose you want 15 ft³ of soil in a bed that is 3 ft long and 2 ft wide. Enter the volume and those two dimensions:
The bed needs to be 2.5 ft deep. This reverse direction is handy whenever the target volume is fixed — like matching a storage limit or a delivery amount.
Reading the result is straightforward: the Volume in cubic feet field is your answer in the default unit, and it stays editable if you want to flip the calculation around. If a number looks too big or too small, double-check that every dimension is in the unit you think it is — 6 inches of depth and 6 feet of depth are very different.
Real-world examples / use cases
1) Filling a vegetable bed with soil
Background: Your new raised bed measures 6 ft by 3 ft, and you plan to fill it 1 ft deep with potting mix.
Input: Length 6, Width 3, Height 1 (all in ft).
What it means: You need 18 cubic feet of mix. With 1.5-cubic-foot bags that’s 12 bags — and our Raised Bed Soil Calculator can turn that into an exact bag count and cost.
2) Will this box fit in the car?
Background: A moving box is 24 in by 18 in by 18 in, and you want its volume before planning the load.
Input: Switch Length, Width, and Height to in and enter 24, 18, 18.
What it means: The box takes up 4.5 cubic feet. Multiplying by the number of boxes gives a quick estimate of how much of the boot or van they’ll fill.
3) Water volume for an aquarium
Background: A 48 in × 12 in × 12 in tank needs filling, and you want the volume in US gallons for dosing and stocking.
Input: Enter the three dimensions in inches, then set “Volume in other units” to US gallons.
What it means: The tank holds about 29.9 US gallons. Remember this is the full rectangular volume — ornaments, substrate, and leaving airspace mean the practical fill is a little less.
4) Mulch for a garden border
Background: A border is 10 ft by 5 ft, and you want a 3-inch layer of mulch.
Input: Length 10, Width 5 (ft), and Height 3 in (the calculator handles the mixed units for you).
What it means: You need 12.5 cubic feet of mulch — about half a cubic yard. The Mulch Calculator can take it from there with bags-versus-bulk pricing.
If you’re measuring water for billing rather than an aquarium, our CCF to Gallons Converter translates hundred-cubic-foot meter readings straight into US gallons.
Common scenarios / when to use
Gardening & landscaping
Estimate soil, mulch, compost, or gravel for beds, planters, and borders. Because depth is usually small (a few inches), mixed-unit entry keeps the math painless.
Moving, storage & shipping
Total the volume of boxes to judge van space, storage-unit sizing, or freight quotes that charge by cubic measure.
DIY & construction
Work out concrete, sand, or gravel for slabs, footings, and paths — handy when a project lists quantities in cubic feet while suppliers sell by the cubic yard.
This calculator works well when:
- You have a box-shaped (rectangular) space and three measurements.
- You want the same volume in several units — gallons, liters, cubic yards, cubic meters — in one go.
- You need to reverse the calculation from a fixed target volume back to a dimension.
It may not be what you need when:
- Your space isn’t rectangular — a cylinder (like a round water tank) or a sphere needs a different volume formula.
- You’re juggling many length units at once before even reaching volume — a dedicated Length Converter keeps those conversions in one place.
- You need area (square feet) rather than volume — that’s a different question entirely.
Tips & best practices
Measure all three sides the same way
The calculator converts units for you, but your answer is only as good as your measurements. Use the inside edges for a box or container, and measure to the same reference point (top, bottom, or water level) on every side.
Use feet-and-inches entry for odd measurements
A wall that is 6 ft 4 in long can be typed directly as 6 ft 4 in — no need to convert 4 inches to a decimal first. The same trick works for meters and centimeters.
Sanity-check with another unit
Switch “Volume in other units” to US gallons or liters as a cross-check: 1 cubic foot is always 7.48052 US gallons and 28.317 liters. If the numbers don’t line up with that feel, re-check your dimensions.
Round up a little when buying materials
Soil, mulch, and gravel settle and compact, and bags rarely line up exactly with your total. For purchases, round up to the next bag or next quarter yard rather than ordering to the last cubic foot.
Pair volume with weight when it matters
Volume alone won’t tell you how heavy a tank or load will be. Our kg to Gallons Converter applies ingredient density if you need to plan around weight.
Calculation method / formula explanation
For a box-shaped object, volume is simply the three dimensions multiplied together. Everything else — unit conversions and reverse solving — follows from that one relationship.
The core formula
Multiply the length, width, and height. If all three are in feet, the result is in cubic feet.
Solving for a missing dimension
Rearrange the formula to isolate the unknown. Given the volume and the other two dimensions:
Converting between length units
The calculator converts every dimension to feet first. Two exact anchors do most of the work:
Converting the volume to other units
Once you have cubic feet, switching to another volume unit is a fixed ratio. The conversions you’ll hit most often:
Where the constants come from
The international foot is defined as exactly 0.3048 meters, so all metric-to-imperial length conversions are exact. Volume ratios like 1 cubic foot = 1,728 cubic inches (12³) and 1 cubic yard = 27 cubic feet (3³) follow from cubing the length ratios. These are fixed definitions, not rounded estimates — only the on-screen preview may round a long decimal for readability.
Related concepts / background info
What is a cubic foot?
A cubic foot is the volume of a cube that is 1 foot long, 1 foot wide, and 1 foot tall. It’s a handy mental image: a cube about the size of a large shoebox. Because one foot is 12 inches, that same cube holds 1,728 cubic inches.
Volume vs. area — don’t mix them up
Area (square feet) measures a flat surface — length × width. Volume (cubic feet) measures how much a space holds — length × width × height. A 10 ft × 10 ft floor is 100 square feet, but the room’s volume depends on its ceiling height. If you only need the floor area, reach for an area tool instead.
Why cubic feet?
Cubic feet are the default volume unit across much of US and UK construction, shipping, and appliance specs — room sizes, refrigerators, HVAC air-flow ratings, and freight measurements all lean on them. Metric countries more often use liters and cubic meters, which this calculator can show just as easily.
The cubic yard connection
Bulk soil, mulch, and gravel are usually sold by the cubic yard. One cubic yard is exactly 27 cubic feet (3 × 3 × 3). If your project comes out to 54 ft³, that’s 2 cubic yards — a useful mental conversion when you’re ordering a delivery.
Why the reverse direction matters
Knowing a target volume and solving for a dimension comes up more than you’d expect — sizing a box to fit a fixed storage space, choosing a planter depth for a set amount of soil, or checking whether a shipment fits a volume limit. That’s why this calculator lets you start from either end.
Frequently asked questions (FAQs)
How many cubic feet are in a cubic yard?
Exactly 27. Since one yard is 3 feet, cubing that gives. You can read your result straight in cubic yards in the “More conversion options” section.
How do I convert cubic feet to gallons?
Multiply by 7.48052 for US gallons (or 6.22884 for UK gallons). For example,. The calculator does this when you set the volume unit to gallons.
How do I calculate cubic feet from inches?
You can enter each dimension in inches directly — the calculator converts them. Or do it by hand: multiply the inches together, then divide by 1,728. A space of 30 × 36 × 25 in is.
What exactly is a cubic foot?
It’s the space inside a cube that is 1 foot on each side — about the size of a large shoebox. It holds 1,728 cubic inches, 7.48052 US gallons, or 28.317 liters.
How much soil do I need for a 4 × 2 ft raised bed?
For 1 ft of depth, you need of soil. At 1.5 ft³ per bag, that’s about 6 bags. Use our Raised Bed Soil Calculator to fine-tune the bag count and cost.
Can I use metric units?
Yes. Length can be entered in meters, centimeters, millimeters, or even meters-and-centimeters as a pair, and the result can be shown in cubic meters, liters, or milliliters — so the tool works just as naturally for metric projects.
What if I know the volume but not a dimension?
Type the volume and the two dimensions you know. The calculator works out the missing one by dividing the volume by the two known dimensions — for example, a 15 ft³ space with a 3 ft × 2 ft footprint needs a depth of 2.5 ft.
My measurements include feet and inches — is that a problem?
Not at all — feet-and-inches entry is the default, so a dimension like “6 ft 4 in” goes straight in without converting anything by hand. If you often add or subtract mixed measurements, our Feet & Inches Calculator is a handy companion for that kind of arithmetic.
Limitations & disclaimer
Limitations
- This calculator assumes a perfect rectangular box. Irregular shapes, tapered containers, rounded corners, and slopes are not modeled — for those, estimate by splitting the shape into rectangular parts or use a purpose-built geometry tool.
- All dimensions must be greater than zero. The result is only as accurate as your measurements, so measure carefully — a small error in one side is multiplied into the volume.
- For soil, mulch, gravel, or concrete, treat the number as an estimate: delivered amounts vary with compaction, settling, and moisture, and suppliers often price bulk loads by the cubic yard. Confirm quantities with your supplier before a large order.
- Results are for planning and reference. For shipping, engineering, or structural decisions, verify against the relevant carrier rules, standards, or a qualified professional.
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