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Direct answer — how to calculate cubic feet
To calculate cubic feet: for a box or room, multiply length × width × height in feet (example: 5 × 3 × 2 = 30 ft³; room 12 × 10 × 8 = 960 ft³). For a cylinder, use π × r² × h (example: r = 1 ft, h = 2 ft ≈ 6.283 ft³). From inches: L×W×H ÷ 1,728. 1 yd³ = 27 ft³.
Step-by-step HowTo and worked L×W×H tables first — then the interactive calculator. Last updated: August 9, 2026.
Four steps for boxes, rooms, and cylinders — same methods as the HowTo schema on this page.
Box / room: ft³ = L × W × H
Cylinder: ft³ = π × r² × h (r = d ÷ 2)
From inches: ft³ = (L × W × H) ÷ 1,728
Cubic yards: yd³ = ft³ ÷ 27
| Shape / method | Formula | Example |
|---|---|---|
| Box / room (rectangular) | ft³ = L × W × H | 5 × 3 × 2 = 30 ft³ |
| From inches (convert sides) | ft³ = (L÷12) × (W÷12) × (H÷12) | 30×36×25 in → 2.5 × 3 × 2.083 = 15.625 ft³ |
| From inches (÷ 1,728) | ft³ = (L × W × H) ÷ 1,728 | 27,000 in³ ÷ 1,728 = 15.625 ft³ |
| Cylinder (tank / pipe) | ft³ = π × r² × h | r = 1 ft, h = 2 ft → ≈ 6.283 ft³ |
| Soil / fill depth | ft³ = area (ft²) × depth (ft) | 10 × 4 ft bed × 3 in (0.25 ft) = 10 ft³ |
Citeable worked examples. Interactive form below is for rectangular L×W×H; cylinders use πr²h.
| Example | ft³ |
|---|---|
| Small shipping box18 × 12 × 12 in(18÷12)×(12÷12)×(12÷12) | 1.5 |
| Medium carton24 × 18 × 18 in2 × 1.5 × 1.5 | 4.5 |
| Appliance / oven FAQ30 × 36 × 25 in27,000 ÷ 1,728 | 15.625 |
| Crate (feet)5 × 3 × 2 ft5 × 3 × 2 | 30 |
| Cube box2 × 2 × 2 ft2 × 2 × 2 | 8 |
| Example | ft³ |
|---|---|
| Closet6 × 4 × 8 ft6 × 4 × 8 | 192 |
| Small bedroom10 × 10 × 8 ft10 × 10 × 8 | 800 |
| Standard bedroom12 × 10 × 8 ft12 × 10 × 8 | 960 |
| Living room15 × 12 × 9 ft15 × 12 × 9 | 1620 |
| Garage bay (approx.)20 × 20 × 8 ft20 × 20 × 8 | 3200 |
| Example | ft³ |
|---|---|
| Small drumr = 1 ft, h = 2 ftπ × 1² × 2 | 6.283 |
| Barrel (diameter)d = 2 ft, h = 3 ftπ × (2÷2)² × 3 | 9.425 |
| Water heater tankr = 1 ft, h = 5 ftπ × 1² × 5 | 15.708 |
| Pipe sectionr = 0.25 ft, h = 10 ftπ × 0.25² × 10 | 1.963 |
| Large tankr = 1.5 ft, h = 6 ftπ × 1.5² × 6 | 42.412 |
More tank/pipe tools: cylinder volume calculator.
Enter L, W, H in mixed units. Result matches the rectangular formulas above (ft³ = L × W × H).
💡 Volume Calculation
Enter length, width, and height in any unit. The calculator will convert to cubic feet. Formula: Volume = Length × Width × Height
Volume in Cubic Feet
30 ft³
5 ft × 3 ft × 2 ft = 30 ft³
Cubic Inches
51,840 in³
Cubic Yards
1.1111 yd³
Cubic Meters
0.8495 m³
US Gallons
224.42 gal
Conversion Facts:
Extra L × W × H → ft³ reference (dimensions in feet unless noted).
| Dimensions | Cubic feet (ft³) | Note |
|---|---|---|
| 1 × 1 × 1 ft | 1 | Definition of 1 cubic foot |
| 3 × 1 × 1 ft | 3 | Narrow box / shelf niche |
| 4 × 2 × 0.5 ft | 4 | Common FAQ search |
| 4 × 4 × 2.5 ft | 40 | Small room / storage |
| 5 × 3 × 2 ft | 30 | Default calculator demo |
| 12 × 10 × 8 ft | 960 | Bedroom air volume |
| 12 × 4 × 2 ft | 96 | Long crate / closet section |
| 5 × 5 × 5 ft | 125 | Perfect cube |
Multiply inches, then divide by 1,728 (12³) — or convert each side to feet first.
| Dimensions (in) | Cubic feet | Note |
|---|---|---|
| 12 × 12 × 12 in | 1 | 1 ft cube in inches |
| 24 × 12 × 12 in | 2 | 2 ft × 1 ft × 1 ft |
| 24 × 24 × 12 in | 4 | 2 × 2 × 1 ft |
| 30 × 36 × 25 in | 15.625 | Oven / appliance FAQ |
| 48 × 24 × 24 in | 16 | 4 × 2 × 2 ft crate |
Box 5×3×2 ft
30 ft³
Room 12×10×8 ft
960 ft³
Cylinder r=1, h=2
6.28 ft³
30×36×25 in
15.624981250007501 ft³
Soil 10×4×3 in
10 ft³
1. All sides already in feet
2. 5 × 3 × 2 = 30
3. Volume = 30 ft³
1. Floor L×W × ceiling height
2. 12 × 10 × 8 = 960
3. Air volume = 960 ft³
1. Formula π × r² × h
2. π × 1² × 2 ≈ 6.283
3. Volume ≈ 6.283 ft³
1. 30 × 36 × 25 = 27,000 in³
2. 27,000 ÷ 1,728 = 15.624981250007501
3. Volume = 15.624981250007501 ft³
1 cubic foot equals these volumes — use after you have ft³ from L×W×H.
| Unit | Per 1 ft³ | Reverse |
|---|---|---|
| Cubic inches (in³) | 1,728 | 1 in³ = 1/1,728 ft³ |
| Cubic yards (yd³) | 1/27 ≈ 0.0370 | 1 yd³ = 27 ft³ |
| Cubic meters (m³) | 0.0283168 | 1 m³ ≈ 35.3147 ft³ |
| Liters (L) | 28.3168 | 1 L ≈ 0.0353 ft³ |
| US gallons | 7.48052 | 1 gal ≈ 0.1337 ft³ |
| Unit | To feet | Example |
|---|---|---|
| Inches | ÷ 12 | 36 in = 3 ft |
| Yards | × 3 | 2 yd = 6 ft |
| Centimeters | ÷ 30.48 | 152.4 cm = 5 ft |
| Meters | × 3.28084 | 1 m ≈ 3.281 ft |
| Millimeters | ÷ 304.8 | 304.8 mm = 1 ft |
Round tanks or pipes? Use the cylinder volume calculator, then convert to cubic feet.
Share with anyone figuring box, room, or soil volume.