24K gold is almost 100% gold, while 18K gold is only 75% gold. The rest is composed of other alloys and metals, such as silver and copper. 24K gold has a brighter, more vibrant appearance than 18K gold. 18K gold also has a richer, warmer look to it.
If you’re uncertain about which type of gold to buy for your wedding or engagement ring, 18K gold is the way to go. It contains 75% gold, so it’s still quite pure, but it’s also more durable than 24K gold.