How to Use the Length Converter

What the Length Converter Does

The Length Converter lets you edit any supported length field and automatically updates every other unit. Whichever box you change becomes the source—there is no separate from or to selector.

Supported Length Units

Six metric and imperial units appear together in one grid: millimeters (mm), centimeters (cm), meters (m), inches (in), feet (ft), and yards (yd).

How to Edit and Convert Values

Type a number in any supported unit. All other length units refresh to match the value you entered. Tap a Common values chip (such as 1 in or 100 cm) to load a starting point quickly. Use Display precision to choose Auto, 2, 3, 4, or 6 decimal places.

Precision and Rounding

Display precision controls how many decimal places appear in the grid—it does not change the underlying conversion relationship. Near critical thresholds, avoid premature rounding in spreadsheets or supplier messages; record raw measurements first.

Common Length Conversions

• 1 inch = 2.54 centimeters
• 10 inches = 25.4 centimeters
• 30 centimeters ≈ 11.81 inches
• 1 foot = 12 inches

Amazon FBA Packaging Dimensions

Amazon US seller tools typically expect outer package dimensions in inches, while many factories provide centimeters or millimeters. Always convert finished packaged length, width, and height—not bare product dimensions—and include mailers, rigid inserts, and protruding seals. This converter changes units only; it does not assign FBA size tiers or fees. For size-tier rules, read Calculation Methodology.

Measuring Packaged Products

Measure the maximum external size of the sellable unit. For soft poly bags, measure at normal fill tension and repeat two or three times.

Deeper packaging guidance is in our Amazon FBA packaging optimization guide.

Common Mistakes

• Converting bare product dimensions instead of finished packaged dimensions.
• Rounding supplier readings too early when a dimension sits near a tier boundary.
• Assuming converted values assign FBA size tiers without using Profit Calculator or Packaging Optimizer.