Cubic Feet Calculator
Volume for boxes, beds, slabs, and round shapes. Five solve modes, material to bags to cost, reverse solving, multi-section totals, and live step-by-step working.
Boxes, rooms, slabs, round tanks, and multi-section jobs in one free tool
A cubic feet calculator finds three-dimensional volume from length, width, and height (or area times depth) and returns results in cubic feet, cubic yards, gallons, and metric units. Enter dimensions in feet, inches, meters, or feet+inches, add quantity and material type, and get waste-adjusted bulk orders, bag counts, weight, cost, and copyable steps using your actual numbers.
Homeowners, movers, landscapers, and contractors all hit the same wall: spreadsheets for unit conversion, then another tab for bags, then a guess on waste. This cu ft calculator keeps box mode, mulch depth, fourteen solid shapes, reverse solving, and shipping dimensional weight on one screen so you are not hopping between thin single-purpose pages. Contractors occassionally mix metric depth with imperial length; per-field units handle that without a seperate spreadsheet. Once you know how much material you need, Invoice Mama makes it simple to turn those quantities into a professional estimate or invoice without retyping line items.
How to Use the Cubic Feet Calculator
Five solve modes, one results panel
- 1
Choose what you are measuring
Box or room, area and depth, round shapes, multiple sections, or work backwards from a known volume.
- 2
Enter dimensions and units
Use mm, cm, m, in, ft, yd, or feet+inches per field. Set quantity, precision, and a context hint for moving, mulch, concrete, or shipping.
- 3
Read volume, material order, and working
Copy cubic feet, cubic yards, US and imperial gallons, bags, weight, cost, dimensional weight, and step-by-step math with your numbers.
Cubic Feet Formula
Same math your teacher used, with job-site units
Shape | Formula |
|---|---|
| Box / room | V = L × W × H |
| Cube | V = a³ |
| Cylinder | V = π r² h |
| Hollow cylinder (pipe) | V = π h (R² − r²) |
| Cone | V = (1/3) π r² h |
| Conical frustum | V = (1/3) π h (R² + Rr + r²) |
| Sphere | V = (4/3) π r³ |
| Hemisphere | V = (2/3) π r³ |
| Capsule | V = π r² ((4/3) r + h) |
| Pyramid (rectangular base) | V = (1/3) L W H |
| Triangular prism | V = (1/2) b h × L |
| Trapezoidal prism | V = (1/2)(a + b) h × L |
| Hexagonal prism | V = (3√3 / 2) s² × h |
| Octagonal prism | V = 2(1 + √2) s² × h |
How to Calculate Cubic Feet from Inches, Yards and Meters
Convert each side to feet before you multiply
Unit | To feet | Example |
|---|---|---|
| Millimeters | ÷ 304.8 | 304.8 mm = 1 ft |
| Centimeters | ÷ 30.48 | 30.48 cm = 1 ft |
| Meters | × 3.280840 | 1 m ≈ 3.28084 ft |
| Inches | ÷ 12 | 12 in = 1 ft |
| Feet | × 1 | 1 ft = 1 ft |
| Yards | × 3 | 1 yd = 3 ft |
| Feet + inches | Parse 5'6", 5 ft 6 in | Mixed imperial entry |
Example: 30 in length → 30 ÷ 12 = 2.5 ft. Multiply 2.5 ft × 3 ft × 2.083 ft ≈ 15.625 cu ft. The step-by-step panel in the tool repeats this logic with your entries so you can paste it into a client email.
How to Calculate Cubic Feet for Round and Irregular Shapes
Cylinder, cone, sphere, and multi-section totals
Round tanks use πr²h. Irregular floors split into rectangles: calculate each piece, then sum. School problems for cones or spheres use the same formulas as construction; only the units change. Worked example (cylinder): 6 ft diameter, 4 ft fill height → radius 3 ft → π × 3² × 4 ≈ 113.1 cu ft ≈ 845 US gallons of water if filled.
How Many Cubic Feet of Mulch, Soil, Gravel or Concrete Do I Need
Area × depth, waste, bags, and cubic yards
Material | Density | Common bags | Typical waste |
|---|---|---|---|
| Mulch | 25 lb/ft³ (20-30) | 2 cu ft bag | 10% typical waste |
| Topsoil | 75 lb/ft³ (70-90) | 1.5 cu ft bag | 10% typical waste |
| Sand | 100 lb/ft³ (90-110) | 0.5 cu ft bag | 8% typical waste |
| Gravel | 95 lb/ft³ (85-105) | 0.5 cu ft bag | 10% typical waste |
| Concrete | 145 lb/ft³ (140-150) | 60 lb bag (~0.45 cu ft), 80 lb bag (~0.6 cu ft) | 5% typical waste |
| Water | 62.4 lb/ft³ (62.4) | Bulk | 0% typical waste |
Depth (in) | Depth (ft) | Sq ft covered | Formula |
|---|---|---|---|
| 1 | 0.0833 | 12.00 | 1 ÷ depth (ft) |
| 2 | 0.1667 | 6.00 | 1 ÷ depth (ft) |
| 3 | 0.2500 | 4.00 | 1 ÷ depth (ft) |
| 4 | 0.3333 | 3.00 | 1 ÷ depth (ft) |
| 6 | 0.5000 | 2.00 | 1 ÷ depth (ft) |
Garden bed: 12 ft × 8 ft = 96 sq ft at 4 in depth → 96 × (4/12) = 32 cu ft → about 1.19 cu yd. Add 10% waste → 35.2 cu ft. At 2 cu ft mulch bags, round up to 18 bags. Pair with our gravel calculator for stone tonnage on the same pad.
Cubic Feet on the Job
Moving, concrete, HVAC air volume, shipping
Moving and storage: thirty medium boxes at 3 cu ft each ≈ 90 cu ft plus furniture blocks. Concrete slab: 12 ft × 20 ft × 0.333 ft (4 in) = 79.9 cu ft = 2.96 cu yd ready-mix. Room air volume: 14 ft × 16 ft × 9 ft = 2,016 cu ft; ventilation still depends on insulation, windows, and climate, so use a real load calculation. Shipping crate: 40×30×28 in = 33,600 in³; at divisor 139, dimensional weight ≈ 242 lb (carriers differ).
Box type | Cu ft (approx.) | Typical use |
|---|---|---|
| Small | 1 | Books, heavy items |
| Medium | 1.5 | Kitchen, office |
| Large | 3 | Linens, lamps |
| Extra large | 4.5 | Light bulky items |
| Wardrobe | 6 | Hanging clothes |
Container | Cu ft (approx.) | Note |
|---|---|---|
| 20 ft standard | 1170 | Internal volume approx. |
| 40 ft standard | 2390 | Internal volume approx. |
| 40 ft high cube | 2690 | Internal volume approx. |
Cubic Feet Reference Tables
Conversions and everyday size anchors
Unit | Factor | Note |
|---|---|---|
| Cubic inches | × 1,728 | 1,728 in³ = 1 ft³ |
| Cubic yards | ÷ 27 | 27 ft³ = 1 yd³ |
| Cubic meters | × 0.0283168466 | From 1 ft = 0.3048 m |
| Liters | × 28.316847 | Derived from m³ |
| US gallons | × 7.480519 | 231 in³ per US gal |
| US quarts | × 29.9221 | 4 US qt per US gal |
| Imperial gallons | × 6.228835 | 4.54609 L per imp gal |
Unit size | Cu ft (approx.) | Note |
|---|---|---|
| 5×5 ft @ 8 ft ceiling | 200 | If fully stackable |
| 5×10 ft @ 8 ft ceiling | 400 | Approximate |
| 10×10 ft @ 8 ft ceiling | 800 | Approximate |
Quick sizes: file box ~1.04 cu ft; a 3 ft cube is 27 cu ft (one cubic yard). Appliance capacities on store tags are usually interior cu ft.
Common measuring mistakes
Save a return trip to the supplier
Mixing inches for depth with feet for length without converting first. Using outside appliance dimensions instead of the interior cavity. Forgetting 5-10% waste on mulch, soil, and gravel. Treating square feet and cubic feet as the same unit on a quote. Ordering bags without rounding up when partial bags are not sold.
Key takeaways
Volume to material to invoice in one pass
Convert every length to feet, then multiply or use area × depth. Bulk orders use cubic yards (divide cu ft by 27). Split irregular rooms into sections and sum volumes. Copy step-by-step working and estimate line items straight into Invoice Mama.
Frequently Asked Questions
Cubic feet, yards, gallons, mulch, concrete, and room volume
How do you calculate cubic feet?
Multiply length × width × height when all three are in feet. Example: 10 ft × 8 ft × 9 ft = 720 cu ft. For mulch or gravel, multiply area in square feet by depth in feet (divide inch depth by 12 first). This cubic feet calculator converts your units, then shows ft³, yd³, gallons, and bags in one view.
How do I calculate cubic feet from inches?
Convert each inch measurement to feet by dividing by 12, then multiply. A 36 in × 24 in × 18 in box: 3 ft × 2 ft × 1.5 ft = 9 cu ft. You can also enter inches per field here and let the tool convert before it multiplies, or type feet+inches like 3'6".
How many cubic feet are in a cubic yard?
One cubic yard equals 27 cubic feet because a yard is 3 feet and 3 × 3 × 3 = 27. Divide your total cubic feet by 27 to order bulk soil, gravel, or concrete by the yard. Example: 54 cu ft ÷ 27 = 2 cu yd.
How do I convert cubic feet to cubic meters?
Multiply cubic feet by 0.0283168466 (from the exact definition 1 ft = 0.3048 m). Example: 100 cu ft × 0.0283168466 ≈ 2.83 m³. Results on this page use the same constant so your conversions match the step-by-step working panel.
How do I calculate the cubic feet of a room?
Measure room length, width, and ceiling height in feet and multiply. A 12 ft × 14 ft room with 8 ft ceilings is 12 × 14 × 8 = 1,344 cu ft of air volume. Use interior dimensions for storage and HVAC planning; load calculations still need proper sizing beyond a single volume number.
How many cubic feet of mulch or soil do I need for a garden bed?
Find bed area in square feet, convert mulch depth from inches to feet (÷ 12), then multiply. A 10 ft × 20 ft bed at 3 inches deep: 200 sq ft × 0.25 ft = 50 cu ft. Add 5-10% extra for waste, then convert to bags or cubic yards for ordering.
How many cubic feet of concrete do I need for a slab, and how many bags is that?
Slab volume is length × width × thickness in feet. A 10 ft × 10 ft slab at 4 inches (0.333 ft) is 33.3 cu ft, or about 1.23 cu yd. A 60 lb bag yields roughly 0.45 cu ft, so divide total cu ft by bag yield and round up. Our concrete calculator handles stairs and tubes too.
How do I convert square feet to cubic feet?
Multiply square feet by depth or height in feet: cu ft = sq ft × ft. You cannot convert area to volume without a thickness. Example: 120 sq ft × 0.5 ft (6 in) = 60 cu ft. Use area-and-depth mode or enter height after you know floor area.
How many gallons are in a cubic foot?
One cubic foot holds about 7.48051948 US liquid gallons (231 cubic inches per gallon). Imperial (UK) gallons differ: about 6.22883546 imperial gallons per cubic foot. This tool labels US and imperial gallons separately so you do not mix them on a quote.
How do I calculate cubic feet for a cylinder or round tank?
Use V = π × r² × h with radius and height in feet. A tank 4 ft in diameter (radius 2 ft) filled to 5 ft high: π × 2² × 5 ≈ 62.83 cu ft. Enter diameter here and toggle radius if you measured from the centerline.
How do I calculate cubic feet for an L-shaped or irregular space?
Split the space into rectangles (or other shapes), calculate each volume, then add them. A room with a 10×12 main area and a 4×6 bump-out both 8 ft high: (120×8) + (24×8) = 1,152 cu ft. Multi-section mode keeps each piece labeled on one page.
What is the difference between cubic feet and square feet?
Square feet measure flat area (length × width). Cubic feet measure three-dimensional volume (length × width × height or area × depth). You need a height or depth in feet to turn sq ft into cu ft. Confusing the two is the most common ordering mistake on mulch jobs.
Should I measure inside or outside dimensions when calculating cubic feet?
For storage, moving, appliances, and tanks, measure inside usable space. Outside dimensions include walls, insulation, and framing that you cannot fill. For building material on a slab, use the pour dimensions your plan calls for, then add waste.
How many cubic feet do I need for a storage unit or move?
Estimate each box or item as a small rectangle, sum cu ft, and compare to your unit. A 5×5 ft unit with 8 ft ceilings is roughly 200 cu ft if stackable (labels vary by facility). Medium moving boxes are often 3-4.5 cu ft each; wardrobe boxes run closer to 6 cu ft.
Related Free Calculators
Volume, area, and quoting tools
- Concrete CalculatorCubic yards, bags, and cost for slabs, stairs, and tubes.
- Square Footage CalculatorFloor area before you add depth for volume.
- Gravel CalculatorTons and cubic yards for base stone and drainage.
- Pipe Volume CalculatorGallons and liters in round pipe runs.
- Drywall CalculatorSheet counts from wall and ceiling area.
- Tile CalculatorTile and grout from sq ft with waste.
- Decking CalculatorBoards and fasteners from deck dimensions.
- Free Estimate MakerTurn quantities into a sendable estimate.
- Invoice GeneratorBill the job with professional line items.
You measured the job on site. Invoice Mama helps you turn cubic feet, bags, and material cost into a professional estimate or invoice without rebuilding the math.