A box volume calculator should be fast, accurate, and respect your privacy. Here's exactly what's under the hood.
Every dimension you enter is converted to SI base units (meters) before any calculation happens. This means a mixed input like "2 ft × 50 cm × 18 in" produces exactly the same result as if you'd converted everything to cm first by hand. Volume is then converted back to the unit you want to display.
Conversion factors are exact ratios from the International System of Units (SI): 1 inch = 0.0254 meters exactly, 1 foot = 0.3048 m, 1 US gallon = 0.003785411784 m³. We don't introduce rounding except at display time.
Dimensional-weight divisors are taken from each carrier's published tariff and verified periodically. Current values used:
Always verify against the carrier's current rate card before billing — these values have changed in the past and may change again. We update them when carriers announce changes, but there can be a lag.
Calculations run at full double-precision floating point (about 15 significant digits). Display values are rounded for readability:
The calculator itself runs entirely in your browser. We don't send your inputs (dimensions, units, results) to any server, and we don't store them. There are no accounts, no logins.
To keep the site free, we use a few third-party services: Google Analytics for traffic measurement, and Google AdSense and Adsterra for advertising. These services may set cookies and process limited information about your visit (pages viewed, approximate location, device type) according to their own privacy policies.
For full details and opt-out instructions, see our privacy policy.
The "Share link" feature works by encoding your inputs into the URL itself (e.g. ?l=30&w=20&h=15&lu=cm), so sharing a calculation means sharing a URL — your data goes in the link, not through our servers.
If a result looks off, a carrier divisor is out of date, or a feature behaves strangely — please get in touch. Calculators are only useful if they're correct.