Solomon Islands is about 1.6 times smaller than Estonia.

Estonia is approximately 45,228 sq km, while Solomon Islands is approximately 28,896 sq km, making Solomon Islands 63.89% the size of Estonia. Meanwhile, the population of Estonia is ~1.2 million people (508,830 fewer people live in Solomon Islands).
Tip: This to-scale comparison of Estonia vs. Solomon Islands uses the Mercator projection, which distorts the size of regions near the poles.