SwapUnits

    Convert

    in² → mm²

    Square Inch
    in²
    Square Millimeter
    645.16
    mm²
    Rounded result (4 decimals max)

    Formula

    1 in² = 645.16 mm²

    Conversion sourcesTap or click to view references

    • The International System of Units (SI) — NIST Special Publication 330

      National Institute of Standards and Technology (NIST). The SI Brochure (SP 330) is the definitive English edition of the BIPM SI tables. NIST’s edition lists the official constants and conversion factors tying inch-pound units to SI, which SwapUnits applies for length, mass, temperature, pressure, volume, and related conversions. See /standards/nist-si-tenfold for the complete decimal multiple/submultiple table. View source · View SI table

    Results update as you type. Swap the direction to convert back from mm² to in².

    Back to main converter

    in² to mm² quick table

    Multiply any row by the same factor to scale results. Use the converter above to enter exact values with your own units.

    Square Inch (in²)Square Millimeter (mm²)
    0.25 in²161.29 mm²
    0.5 in²322.58 mm²
    1 in²645.16 mm²
    2 in²1,290.32 mm²
    5 in²3,225.8 mm²
    10 in²6,451.6 mm²
    25 in²16,129 mm²
    100 in²64,516 mm²

    mm² back to in²

    Keep the reciprocal handy when double-checking calculations or undoing a conversion.

    Square Millimeter (mm²)Square Inch (in²)
    0.25 mm²0.0004 in²
    0.5 mm²0.0008 in²
    1 mm²0.0016 in²
    2 mm²0.0031 in²
    5 mm²0.0078 in²
    10 mm²0.0155 in²
    25 mm²0.0388 in²
    100 mm²0.155 in²

    Explore more area converter & surface reference

    in² → cm²

    Convert into Square Centimeter without leaving SwapUnits.

    in² → ft²

    Convert into Square Foot without leaving SwapUnits.

    in² → yd²

    Convert into Square Yard without leaving SwapUnits.

    in² → m²

    Convert into Square Meter without leaving SwapUnits.

    in² → acre

    Convert into Acre without leaving SwapUnits.

    in² → ha

    Convert into Hectare without leaving SwapUnits.

    Compare all area converter & surface reference

    View the full unit roster, charts, and tips for Area Converter & Surface Reference conversions.

    Open category guide