Square Millimeters to Hectares: the quick answer
1 mm² = 1 × 10⁻¹⁰ ha
1 square millimeter equals 1 × 10⁻¹⁰ hectares
To convert square millimeters to hectares, multiply the value by 1 × 10⁻¹⁰. To go the other way, multiply hectares by 10,000,000,000 to get square millimeters.