# Square Inches to Square Millimeters Converter

Enter the area in square inches below to get the value converted to square millimeters.

## Result in Square Millimeters:

1 sq in = 6.4516 sq cm

Do you want to convert square millimeters to square inches?

## How to Convert Square Inches to Square Millimeters

To convert a measurement in square inches to a measurement in square millimeters, multiply the area by the following conversion ratio: 645.16 square millimeters/square inch.

Since one square inch is equal to 645.16 square millimeters, you can use this simple formula to convert:

square millimeters = square inches × 645.16

The area in square millimeters is equal to the area in square inches multiplied by 645.16.

**For example,**here's how to convert 5 square inches to square millimeters using the formula above.

### How Many Square Millimeters Are in a Square Inch?

There are **645.16** square millimeters in a square inch, which is why we use this value in the formula above.

1 sq in = 645.16 sq mm

Square inches and square millimeters are both units used to measure area. Keep reading to learn more about each unit of measure.

## What Is a Square Inch?

One square inch is equivalent to the area of a square with sides that are each 1 inch in length. One square inch is equal to 1/144 of a square foot or 1/1,296 of a square yard.

The square inch is a US customary and imperial unit of area. A square inch is sometimes also referred to as a square in. Square inches can be abbreviated as *sq in*, and are also sometimes abbreviated as *in²*. For example, 1 square inch can be written as 1 sq in or 1 in².

Learn more about square inches.

## What Is a Square Millimeter?

One square millimeter is equivalent to the area of a square with edges that are each 1 millimeter in length. One square millimeter is equal to 0.00155 square inches or 1/100 of a square centimeter.

The square millimeter, or square millimetre, is a multiple of the square meter, which is the SI derived unit for area. In the metric system, "milli" is the prefix for thousandths, or 10^{-3}. A square millimeter is sometimes also referred to as a square mm. Square millimeters can be abbreviated as *sq mm*, and are also sometimes abbreviated as *mm²*. For example, 1 square millimeter can be written as 1 sq mm or 1 mm².

Learn more about square millimeters.

## Square Inch to Square Millimeter Conversion Table

Square Inches | Square Millimeters |
---|---|

1 sq in | 645.16 sq mm |

2 sq in | 1,290 sq mm |

3 sq in | 1,935 sq mm |

4 sq in | 2,581 sq mm |

5 sq in | 3,226 sq mm |

6 sq in | 3,871 sq mm |

7 sq in | 4,516 sq mm |

8 sq in | 5,161 sq mm |

9 sq in | 5,806 sq mm |

10 sq in | 6,452 sq mm |

11 sq in | 7,097 sq mm |

12 sq in | 7,742 sq mm |

13 sq in | 8,387 sq mm |

14 sq in | 9,032 sq mm |

15 sq in | 9,677 sq mm |

16 sq in | 10,323 sq mm |

17 sq in | 10,968 sq mm |

18 sq in | 11,613 sq mm |

19 sq in | 12,258 sq mm |

20 sq in | 12,903 sq mm |

21 sq in | 13,548 sq mm |

22 sq in | 14,194 sq mm |

23 sq in | 14,839 sq mm |

24 sq in | 15,484 sq mm |

25 sq in | 16,129 sq mm |

26 sq in | 16,774 sq mm |

27 sq in | 17,419 sq mm |

28 sq in | 18,064 sq mm |

29 sq in | 18,710 sq mm |

30 sq in | 19,355 sq mm |

31 sq in | 20,000 sq mm |

32 sq in | 20,645 sq mm |

33 sq in | 21,290 sq mm |

34 sq in | 21,935 sq mm |

35 sq in | 22,581 sq mm |

36 sq in | 23,226 sq mm |

37 sq in | 23,871 sq mm |

38 sq in | 24,516 sq mm |

39 sq in | 25,161 sq mm |

40 sq in | 25,806 sq mm |

## More Square Inch & Square Millimeter Conversions

- square inches to square miles
- square inches to acres
- square inches to square yards
- square inches to square feet
- square inches to square kilometers
- square inches to square meters
- square inches to square centimeters
- square inches to hectares
- square inches to ares
- square miles to square millimeters
- acres to square millimeters
- square yards to square millimeters
- square feet to square millimeters
- square kilometers to square millimeters
- square meters to square millimeters
- square centimeters to square millimeters
- hectares to square millimeters
- ares to square millimeters