Square Feet to Square Miles: the quick answer
1 ft² = 3.58701 × 10⁻⁸ mi²
1 square foot equals 3.58701 × 10⁻⁸ square miles
To convert square feet to square miles, multiply the value by 3.58701 × 10⁻⁸. To go the other way, multiply square miles by 27,878,400 to get square feet.