Papua New Guinea is about 2.6 times bigger than Oklahoma.

Oklahoma is approximately 177,847 sq km, while Papua New Guinea is approximately 462,840 sq km, making Papua New Guinea 160% larger than Oklahoma. Meanwhile, the population of Oklahoma is ~3.8 million people (5.8 million more people live in Papua New Guinea).
Tip: This to-scale comparison of Oklahoma vs. Papua New Guinea uses the Mercator projection, which distorts the size of regions near the poles.