Cubic Feet Calculator

Picture this: you are standing in front of a half-finished raised garden bed, wondering how many bags of soil to buy. Or you are pricing a moving truck and the rental site keeps asking for cubic feet. Or you are sizing a new fridge and the spec sheet quotes “20.5 ft³” with no idea what that actually means.

Cubic feet shows up in dozens of real-world decisions — bagged mulch, ready-mix concrete, shipping rates, HVAC sizing, appliance shopping, sauna heaters, storage units. Get the number right and you save money, time, and a return trip to the supplier. Get it wrong and you over-order, under-order, or pay for shipping volume you do not need.

This calculator and the guide below give you both: a free tool that handles nine shapes and thirty unit conversions, and the formulas behind it so you can verify any answer. Whether you are estimating soil for a 4 × 8 ft bed, loading a 26-foot moving truck, or comparing two refrigerators, you will finish with a number you can trust and use.

What exactly is a cubic foot?

A cubic foot (ft³) is a three-dimensional unit of volume equal to a cube that measures exactly one foot on every side. Picture a perfect square box, one foot wide, one foot deep, and one foot tall — that is one cubic foot. It contains 1,728 cubic inches (since 12 × 12 × 12 = 1,728), about 28.32 liters of water, and roughly 7.48 US gallons.

The cubic foot belongs to the imperial and US customary systems and remains the dominant unit of volume across construction, real estate, shipping, and household appliances in the United States. Outside the US, the metric cubic meter (m³, also called CBM) is more common, but cubic feet still appear in international shipping quotes, freight rates, and engineering specs.

Why volume is measured in cubic units

Volume is the amount of space something occupies, and space is three-dimensional — length, width, and height. When you multiply three lengths together (each in the same unit), the result inherits the unit raised to the third power. Multiply three measurements in feet and you get a result in feet³ (read as "feet cubed" or "cubic feet"). The exponent isn't decoration — it tells you the result is a 3D quantity, not a flat area or a single distance.

A cubic foot in everyday terms

One cubic foot is roughly the size of a microwave oven, a thick stack of standard office paper, a basketball plus an inch of clearance on every side, or a typical kitchen-sink dish drying rack. Most countertop appliances are between 1 and 3 cubic feet of interior space. A standard residential refrigerator falls between 18 and 26 cubic feet of total interior volume.

Why calculate cubic feet? Real-world applications

Knowing how to calculate cubic feet is not just a math exercise — it's a practical skill that saves you money on materials, prevents costly under- or over-ordering, and helps you plan projects with confidence. Here is where it matters most.

Material estimation (concrete, soil, mulch, gravel)

Bulk materials are sold by the cubic foot, cubic yard, or by the bag (with bag volumes given in cubic feet). You need cubic feet to figure out how much to order:

• Concrete for slabs and footings: a 4-inch-thick 10 × 10 ft slab is 10 × 10 × 0.333 = 33.3 ft³, which is 1.23 yd³ or about 56 of the standard 80 lb bags. See our concrete cubic feet calculator.
• Soil for raised beds: a 4 × 8 × 1 ft bed needs exactly 32 ft³, or 16 of the typical 2 ft³ bagged soil products. Try the raised bed soil calculator.
• Mulch for landscaping: cover 200 ft² to a 3-inch depth and you need 50 ft³, which is 25 of the 2 ft³ bags or about 1.85 yd³.
• Gravel for driveways: convert ft³ to tons using ~1.4 tons per yd³ (or ~105 lbs per ft³) — the gravel calculator handles it for you.

Shipping, freight, and logistics

Carriers price freight by the greater of actual weight or dimensional (volumetric) weight, and dimensional weight is calculated from cubic feet (or CBM). A package's dim weight uses a divisor — 166 in³/lb for domestic UPS/FedEx — meaning a 1 ft³ box (1,728 in³) bills as roughly 10.4 lbs even if it's feather-light. For ocean freight, CBM is the universal unit; 1 CBM ≈ 35.31 ft³.

Storage units and moving trucks

Storage facilities advertise units by floor footprint, but the usable space is cubic. A 10 × 10 ft unit with an 8 ft ceiling holds 800 ft³ — about a 2-bedroom home of furniture if you stack efficiently. Moving truck capacity is published in cubic feet: a 10 ft truck ≈ 380 ft³, a 17 ft truck ≈ 850 ft³, and a 26 ft truck ≈ 1,700 ft³. Our moving cubic feet calculator takes a checklist of items and suggests the right truck size automatically.

HVAC, air, and room volume

Heating, cooling, and ventilation engineers size systems against room volume in cubic feet. For a target of N air changes per hour (ACH), the required airflow in CFM (cubic feet per minute) is (room ft³ × ACH) / 60. A 12 × 14 × 9 ft bedroom is 1,512 ft³; at 4 ACH it needs ~101 CFM of supply air. Sauna heaters use roughly 1 kW per 50 ft³ of room volume — see the sauna heater sizing tool.

Appliances (refrigerator, freezer, microwave, oven)

Appliance capacity is almost always quoted in cubic feet of usable interior space. A typical full-size fridge runs 18–26 ft³, a chest freezer 5–22 ft³, a microwave 0.7–2.2 ft³, and an oven 4–6 ft³. To measure your own, multiply the interior length, width, and height in inches, then divide by 1,728.

Real-world case studies

The landscaper's mulch order

A landscaper estimates mulch for a curved 240 ft² border at 3 inches deep. Three inches is 0.25 ft, so volume is 240 × 0.25 = 60 ft³, which works out to 2.22 yd³, or 30 of the 2 ft³ bags. By calculating cubic feet first, the landscaper avoids the common error of over-ordering by a yard (worth ~$50) or under-ordering and making a second trip.

E-commerce shipping optimization

An online seller ships ceramic mugs in 12 × 8 × 5-inch boxes — that's 480 in³ or 0.278 ft³. By switching to a 10 × 7 × 4-inch box (280 in³, 0.162 ft³), the dimensional weight drops from 2.89 lbs to 1.69 lbs per box, cutting carrier billing weight by 40% across thousands of shipments per month. Cubic-feet thinking turns packaging into a profit lever.

A DIY concrete slab project

A homeowner pours a 12 × 12 ft patio at 4 inches thick. Volume = 12 × 12 × 0.333 ≈ 48 ft³, or 1.78 yd³. The local supplier sells in 0.25-yd³ increments, so the homeowner orders 2 yd³ (54 ft³), giving a sensible 12% buffer for spillage and edge variation. Without the calculation, "I'll just get a couple yards" easily becomes 50% over- or under-ordered.

How to use our cubic feet calculator

The calculator at the top of this page is built for speed. Here's the fastest path from "I have dimensions" to "I have an answer in every unit I need."

Step-by-step walkthrough

1. Pick a shape from the tabs (Rectangle, Cylinder, Sphere, Cone, Triangular Prism, or Irregular). Most rooms, boxes, and slabs are rectangles — that's the default.
2. Enter your dimensions. Each input has its own unit dropdown, so you can mix inches, feet, yards, centimeters, and meters in the same calculation.
3. (Optional) Add cost per cubic foot to get an instant material cost estimate alongside the volume.
4. Read the result panel: cubic feet (large), then conversions to yd³, m³, in³, liters, gallons, and CBM. If you entered cost, total dollars appear in green.
5. Save or share. Use Copy to put the result on your clipboard, Share to copy a URL with the dimensions baked in (so the same calculation reopens later), or Print for a job-site reference.

Visualizing your volume in 3D

The right-side 3D viewer renders your entered shape proportionally, with orbit controls so you can rotate, pan, and zoom. It's the fastest way to catch a "wait, that doesn't look right" before ordering 5 yards of concrete based on a typo.

"What if?" cost and space scenarios

Try changing one input by 6 inches and watch the cost and bag count update in real time. This is how you find optimal raised-bed depths, shipping-box sizes, and cabinet dimensions without solving anything by hand.

Manual cubic feet calculation: formulas for every shape

The six formulas below are the standard solid-geometry equations used in engineering and construction worldwide. Where you see π (pi), use 3.14159 for pencil-and-paper math; the calculator uses the full machine-precision value.

Every formula below assumes all inputs are already in feet. If yours aren't, see the next section on unit conversion.

Cuboid / rectangle (L × W × H)

Cylinder (π · r² · H)

If you only have the diameter, divide it by 2 first to get the radius.

Sphere ((4/3) · π · r³)

Cone ((1/3) · π · r² · H)

Triangular prism

Irregular shapes (segmentation method)

Real rooms, beds, and ponds rarely come in textbook shapes. The reliable approach is segmentation: split the irregular form into smaller rectangles, cylinders, or triangles you can calculate, find the volume of each piece, and add them up. An L-shaped room of 12 × 8 ft plus a 6 × 4 ft alcove, both 9 ft tall, becomes (12 × 8 × 9) + (6 × 4 × 9) = 864 + 216 = 1,080 ft³. Use the irregular shape calculator to add segments without doing the math yourself.

Calculating cubic feet from other units

The cleanest method is to convert each linear measurement to feet first, then apply the formula. Here are the four most common starting units.

From inches to cubic feet

Either convert each measurement to feet (divide by 12) and then multiply, or multiply all three measurements in inches first and divide the product by 1,728. Both methods give the same answer.

From meters to cubic feet

Compute the volume in cubic meters first, then multiply by 35.3147 to get cubic feet. (Equivalently, multiply each linear meter by 3.28084 to convert to feet before multiplying.)

From yards to cubic feet

Multiply each yard measurement by 3 to convert to feet, then apply the formula. Equivalently, the volume in cubic yards times 27 gives cubic feet.

From centimeters to cubic feet

Multiply each centimeter measurement by 0.0328084 to convert to feet, then apply the formula. Or compute volume in cubic centimeters and multiply by 0.0000353147.

Cubic feet vs. square feet vs. cubic yards

These three units get confused constantly, often with expensive consequences when ordering bulk materials. Here's the clean distinction:

The fast mnemonic: area covers a floor, volume fills a box. Square feet × depth in feet = cubic feet. And there are always 27 cubic feet in one cubic yard.

Cubic feet unit conversion cheatsheet

Common mistakes & how to avoid them

1. Mixing units mid-calculation. Multiplying 5 ft × 36 in × 2 ft gives 360 — but that's neither cubic feet nor cubic inches. Always convert everything to one unit first.
2. Confusing area with volume. Square feet × depth in feet = cubic feet. If you skip the depth, you're ordering material for a 1-foot-thick layer whether you wanted that or not.
3. Ignoring compaction and settling. Loose soil, gravel, and mulch lose 5–10% volume when delivered or watered in. Add a buffer.
4. Forgetting dead space. A 1,000 ft³ truck doesn't hold 1,000 ft³ of furniture — boxes have gaps, sofas have legs, and irregular shapes leave air. Plan on ~80% effective use.
5. Treating a cylinder as a cuboid. A cylindrical pillar is not length × width × height — it's π · r² · H, which is about 78.5% of the bounding-box volume.
6. Using outside dimensions for interiors. Refrigerator cabinets, coolers, and shipping crates have walls. Always measure the inside.
7. Double-counting overlapping segments. When splitting an L-shape, make sure your two rectangles don't share a region.
8. Rounding too early. Round only at the final answer; round intermediate steps and the error compounds.

Expert tips for accurate cubic feet calculations

• Double-check every measurement. A 6-inch error on each side of a 10 × 10 × 10 ft room is a 16% volume error.
• Pick one unit and stick to it. Convert every length to feet before you multiply, or every length to inches and divide by 1,728 at the end. Mixing inches and feet inside the same multiplication is the most common cubic feet error.
• Segment irregular shapes. Break L-shaped rooms, curved beds, and stepped walls into rectangles, cylinders, or triangles. Calculate each piece separately, then sum. The irregular shape calculator does this automatically.
• Use a laser distance measurer for any distance over 10 ft. Tape measures sag and lie.
• Round up for materials. Bulk concrete, soil, and gravel cost more in lost trips than in the small amount you don't use.
• Account for material settling. Add 5–10% to soil, mulch, and gravel orders to allow for compaction.
• Add a buffer for shipping dead space. Plan on 15–20% extra cubic feet over the sum of item volumes.
• Distinguish net from gross volume. Net is the item; gross is the packaged item — carriers care about gross.
• Document dimensions. A short spreadsheet of room or container dimensions beats remeasuring six months later.
• Use online converters for tricky units. Mental math on acre-feet, board-feet, or UK gallons is asking for trouble. Browse the converter index for every common conversion.

Cubic feet glossary — terms you need to know

Definitions for the units and concepts that come up across every cubic-feet calculation. Each term links to an authoritative source where applicable.

Cubic foot (ft³)

The volume of a 1 ft × 1 ft × 1 ft cube. Equal to exactly 1,728 in³ and approximately 0.0283168 m³ or 7.48052 US gallons.

Cubic yard (yd³)

The volume of a 3 ft × 3 ft × 3 ft cube — exactly 27 cubic feet. The standard ordering unit for soil, gravel, and concrete in the US.

Cubic meter (m³)

The SI volume unit. 1 m³ ≈ 35.3147 ft³. In international shipping the same unit is called CBM (cubic meter); the two are interchangeable.

Board foot (bf)

A lumber-only unit equal to 1 ft × 1 ft × 1 in (144 in³ = 1/12 of a cubic foot). Used to price hardwood and dimensional lumber.

CBM

Cubic meter, in shipping context. A standard 20-ft container holds about 33 CBM (≈ 1,170 ft³); a 40-ft container holds about 67 CBM (≈ 2,390 ft³).

Volumetric weight

Also called dimensional or DIM weight. Carriers bill the greater of actual weight and volumetric weight, where volumetric weight = (L × W × H in inches) ÷ DIM divisor (typically 139 for domestic US, 166 for international).

ACH (air changes per hour)

How many times a room's air volume is exchanged each hour. ACH = (CFM × 60) ÷ cubic feet of room. Bedrooms target 4–6 ACH; kitchens 7–8; bathrooms 8–10.

CFM (cubic feet per minute)

Airflow rate. Multiply CFM by 60 and divide by room volume to get ACH. A typical bathroom fan moves 50–110 CFM.

BTU per cubic foot

Heat content of a fuel gas. Pipeline natural gas is approximately 1,037 BTU/ft³; propane is approximately 2,516 BTU/ft³. Used for sizing burners and meters.

Dry quart vs liquid quart

Two different US units. 1 ft³ = 25.71 dry quarts (used for soil and mulch) but 29.92 liquid quarts (used for fluids). Always check the bag label.

Frequently asked questions

Start calculating with confidence

You now have everything you need to calculate cubic feet for any shape, any unit, and any project. The calculator above handles the math; the formulas in this guide let you verify any answer; the case studies show what the numbers look like in real money saved.

When you open the calculator, you choose a shape, enter dimensions in whichever unit is on your tape measure, and read the result in cubic feet — plus thirty other units side by side. The 3D viewer draws what you typed so you can sanity-check the shape before ordering. The cost estimator turns volume into a dollar figure when you know the price per cubic foot.

Try it now. Enter your length, width, and height at the top of the page. If you have a more specialized job — soil for a raised bed, concrete for a slab, mulch for a border, gas for a sauna heater — jump straight to a topic-specific calculator that pre-loads the right defaults. You can also browse the use-case pages for concrete, soil, moving, or shipping — each one pre-loads bag counts, truck sizes, and freight-rate factors specific to that project type.