It is believed that shape of Earth is not a perfect sphere but an oblate spheroid. In Pancasiddhāntika of Varāhamihira, given value of circumference of Earth is 3200 yojanas. Let's find out the value of circumference of Earth in kilometers.
1 yojana = 8 miles
1 mile = 5280 foot
1 feet = 12 inch
1 inch = 2.54 cm
1 yojana = (8×5280×12×2.54) cm
= 12.87 km
Circumference of Earth = 3200 yojanas = 3200×12.87 = 41184 km
Thus, the Radius of Earth = 41184/2×3.14 = 6557.9 km
Thus, the Radius of Earth = 41184/2×3.14 = 6557.9 km