Square Miles to Square Kilometers (mi² to km²) Converter

Square Miles to Square Kilometers Converter

This tool converts square miles to square kilometers, the international standard for measuring large geographic areas.

1 square mile = 2.59 square kilometers. Texas (268,596 mi²) equals 695,662 km², comparable to Myanmar. Alaska (663,300 mi²) equals 1.72 million km².

Why Convert

International Audiences

Readers outside the US expect metric units, so convert US data to km² for clarity.

Scientific Research

Academic journals require SI units, and global geographic databases use km².

How to Use the Converter

Enter the Value

Enter the US geographic area in square miles in the left field.

Read the Result

The metric result in square kilometers appears instantly on the right.

Copy or Swap

Copy the value for papers or reports, or swap to convert square kilometers back to square miles.

Quick estimate: multiply mi² by 2.5. For 100 mi²: 100 × 2.5 = 250 km². The exact answer is 259 km² — close enough for a fast comparison.

Converter Features

Instant Real-Time Conversion

The result updates the moment you type. There is no calculate button, so you can compare several values in seconds.

Bidirectional Swap

Press the swap button between the two fields to reverse the direction instantly, without reloading the page or re-typing.

Searchable Unit Picker

Each unit dropdown has a search box, so you can switch to any other area unit and convert in a different direction whenever you need.

One-Click Copy

A copy button sits beside each field. Tap it to send the value straight to your clipboard for reports, listings, or spreadsheets.

Quick Reference & Unit Info

A built-in quick-reference grid and unit info cards show common values and where each unit is used, right below the converter.

Mobile-Optimized Design

Large touch targets and a responsive layout make conversions easy on a phone, whether on-site, in a store, or on the go.

Reference Values

Square Miles	Square Kilometers
1 mi²	2.59 km²
10 mi²	25.9 km²
100 mi²	259 km²
1,000 mi²	2,590 km²
10,000 mi²	25,900 km²
100,000 mi²	259,000 km²

Frequently Asked Questions

How do I convert square miles to square kilometers?

Multiply square miles by 2.59. For example, 100 mi² × 2.59 = 259 km².

Why should I convert to square kilometers?

Scientific journals, international organizations, and most of the world use km². Converting ensures your data is accessible globally and compatible with other research.

What's the quick mental math for mi² to km²?

Multiply by 2.5 for a quick estimate. For 100 mi²: 100 × 2.5 = 250 km². The exact answer is 259 km² — close enough for quick comparisons.

How does the US compare to other countries in km²?

The contiguous US (3.12M mi²) = 8.08M km². This makes it comparable to Brazil (8.51M km²) or slightly smaller than China (9.6M km²).

Do scientific papers accept square miles?

Generally no. International scientific publications require SI units, so convert to km² for submission, even when studying US geography.

Square Miles to Square Kilometers