Oklahoma is about 2,916 times bigger than San Marino.

San Marino is approximately 61 sq km, while Oklahoma is approximately 177,847 sq km, making Oklahoma 291,452% larger than San Marino. Meanwhile, the population of San Marino is ~34,682 people (3.7 million more people live in Oklahoma).
Tip: This to-scale comparison of San Marino vs. Oklahoma uses the Mercator projection, which distorts the size of regions near the poles.