Cubic Inch Formula
Volume (in³) = Length (in) × Width (in) × Height (in)
To ft³: in³ ÷ 1,728
To m³ (CBM): in³ ÷ 61,023.7
To ft³: in³ ÷ 1,728
To m³ (CBM): in³ ÷ 61,023.7
Why Cubic Inches Matter in Shipping
Cubic inches are used primarily in US domestic parcel and courier shipping. FedEx, UPS and USPS use dimensional weight formulas based on cubic inches:
Dimensional Weight (lbs) = L(in) × W(in) × H(in) ÷ 139 (FedEx/UPS domestic)
For international: L × W × H ÷ 166
For international: L × W × H ÷ 166
If your package's dimensional weight exceeds its actual weight, you'll be charged based on dimensional weight — making this calculation essential for cost estimation.
Frequently Asked Questions
1 cubic foot = 1,728 cubic inches (12 × 12 × 12). To convert ft³ to in³, multiply by 1,728. To convert in³ to ft³, divide by 1,728.
For FedEx/UPS US domestic: Dim Weight (lbs) = (L × W × H in inches) ÷ 139. For international: ÷ 166. For air freight using CBM: CBM × 6,000 = vol. weight in kg.