You need 32GB for SolidWorks with 500-part assemblies.

Yes, 16GB will help over 8GB, but 32GB is where you want to be.

SolidWorks with assemblies that size chews through RAM like candy. 8GB is a bottleneck even for light use. Jumping to 16GB will stop the immediate swapping and crashes, but you’ll still hit slowdown when rebuilding mates, running simulations, or keeping multiple documents open. 32GB gives you comfortable headroom for the assembly plus whatever else your OS and browser are doing.

If your motherboard supports it, go straight to 32GB. The price difference between 16GB and 32GB is small relative to the productivity gain. Future proof it—next year you’ll have 800-part assemblies.