Box Volume Calculator
cubic feet, inches, liters & gallons
Enter a box’s length, width and height in any unit — even mixed, like 2 ft × 18 in × 30 cm — and get its volume in cubic feet, cubic inches, liters, gallons and cubic meters at once.
Box walls — inside vs outside size
Flute thicknesses are typical values — board varies by maker, so measure yours if it matters. Building a cabinet? The speaker box volume calculator also takes the driver and port displacement out.
How to calculate the volume of a box.
A box (a rectangular prism, or cuboid) holds length × width × height. The only rule is that all three sides use the same unit — which this calculator handles for you.
- Measure the three sides. Use the inside of the box for how much it holds, the outside for shipping.
- Use one unit for all three, or pick a unit per side above and let the calculator convert.
- Multiply them together. Inches give cubic inches (in³), centimeters give cubic centimeters (cm³).
- Convert if you need to: in³ ÷ 1,728 = ft³ · ft³ × 7.48 = US gallons · cm³ ÷ 1,000 = liters.
Three boxes, worked out.
Inches → cubic feet
2,160 ÷ 1,728 = 1.25 ft³
= 35.4 L · 9.35 US gal
A typical shipping carton. Open in the calculator →
Centimeters → liters
30,000 ÷ 1,000 = 30 L
= 1.06 ft³
A medium storage box. Open in the calculator →
Mixed units
= 24 × 18 × 11.81 in = 5,102 in³
= 2.95 ft³ · 83.6 L
Each side in a different unit. Open in the calculator →
Volume of common box sizes.
Tap a size to load it into the calculator.
| Box (L × W × H) | Cubic inches | Cubic feet | Liters | US gallons |
|---|---|---|---|---|
| 12 × 12 × 12 in | 1,728 | 1 | 28.3 | 7.48 |
| 16 × 12 × 12 in | 2,304 | 1.333 | 37.8 | 9.97 |
| 18 × 14 × 12 in | 3,024 | 1.75 | 49.6 | 13.09 |
| 18 × 18 × 16 in | 5,184 | 3 | 85.0 | 22.44 |
| 18 × 18 × 24 in | 7,776 | 4.5 | 127.4 | 33.66 |
| 20 × 20 × 20 in | 8,000 | 4.63 | 131.1 | 34.63 |
| 24 × 24 × 24 in | 13,824 | 8 | 226.5 | 59.84 |
| USPS Priority Mail Flat Rate boxes (inside dimensions) | ||||
| USPS Small Flat Rate Box 8 5/8 × 5 3/8 × 1 5/8 in (inside) | 75.3 | 0.044 | 1.23 | — |
| USPS Medium Flat Rate Box 1 11 × 8 1/2 × 5 1/2 in (inside) | 514.2 | 0.298 | 8.43 | — |
| USPS Medium Flat Rate Box 2 13 5/8 × 11 7/8 × 3 3/8 in (inside) | 546.1 | 0.316 | 8.95 | — |
| USPS Large Flat Rate Box 12 × 11 3/4 × 5 1/2 in (inside) | 775.5 | 0.449 | 12.71 | — |
USPS inside dimensions from usps.com. Flat Rate boxes are priced by box, not by weight or dimensional weight. See all 155 standard box sizes →
Measuring something other than a box? We have calculators for concrete slabs and footings, mulch and gravel by depth, cargo van capacity, freezer capacity, aquariums, swimming pools and moving estimates — all ten →
Box volume questions.
How do you calculate the volume of a box?
How do I convert cubic inches to cubic feet?
How many gallons are in a cubic foot?
How do I convert cubic centimeters to liters?
Should I measure the inside or the outside of the box?
Can I use different units for each side?
Can I enter fractions?
Is box volume the same as dimensional weight?
More answers on the full FAQ and the formula page.
More than just volume.
Shipping & DIM weight
Volumetric weight with FedEx, UPS, USPS, DHL and Parcelforce presets, plus carrier size checks.
Multi-box batch mode
Add as many boxes as you need, with quantity multipliers and CSV export. For movers, FBA, and warehouses.
Formula & examples
The full breakdown of how V = l × w × h works, with worked examples and conversion tables.
Frequently asked
What's a cuboid, when do liters apply, can I use fractions — the questions everyone actually has.
Tailored for what you're measuring.
🐠 Aquarium
Tank volume in gallons and liters, with stocking rules and substrate notes.
🌱 Garden soil
Soil for raised beds in cubic yards, plus how many bags you'll need.
🏊 Swimming pool
Pool volume in gallons with chlorine-dosing reference numbers.
📦 Moving estimate
Total cubic feet with a truck-size reference for U-Haul and Penske.
🚪 Appliance fit
Will the fridge fit through the doorway? Diagonal-based fit check.
Specialized calculators.
Carrier-specific dimensional weight calculators, shipping volume tools, and unit converters — each built on the same engine as the main calculator above.
📦 DIM Weight
Dimensional weight for FedEx, UPS (Daily & Retail), USPS, DHL, Parcelforce and air freight.
🚢 CBM Calculator
Cubic meters for ocean freight, with container and pallet capacity reference.
📦 FedEx DIM
FedEx dimensional weight (139 divisor) with FedEx’s 2026 surcharge amounts.
📦 UPS DIM
UPS Daily (139) and Retail (166) divisors, plus UPS Additional Handling and Large Package checks.
📋 Batch mode
Total volume across many boxes at once — CSV export, presets, instant sums.
↔ cm³ to Liters
Cubic centimeters ⇌ liters converter. 1 L = 1,000 cm³ (exact).
↔ ft³ to Gallons
Cubic feet to US gallons and UK imperial gallons (both at once).
⧉ Embed it
Put this calculator on your own site — free, no signup, one iframe snippet.
→ All use cases
See all 10 specialized calculators — aquarium, soil, pool, concrete, more.