How big is a walnut in centimeters?

The size of a walnut can vary depending on the specific type of walnut, but on average, a walnut is roughly 3-4 centimeters in diameter. This measurement is taken at the widest part of the walnut, which is typically the equatorial region. It's important to note that this measurement can fluctuate slightly based on factors such as the maturity and variety of the walnut.