Both 1-gram and 1-ounce gold bars can be a smart investment, but one may be the better option in today's market.

But one of the more popular options is gold bars, which are available in different sizes, including 1-gram and 1-ounce gold bars.

There are many sizes of gold bars to choose from. Here's how to decide if 1-gram bars are a good fit for you.

Costco's largest gold product is a 100-gram bar from PAMP Suisse that last sold for $7,599.99. The jumbo-sized bar was briefly available this week, but sold out in less than a day.

Costco has been selling out of its one-ounce gold bars — priced at $1,949.99 and $1,979.99 — and are eligible for the 2% cash back that comes with an Executive Member card.

If you've been itching to get into the gold market at Costco, the retailer has put a limit on how many of its gold bars you can buy.

Korea's convenience stores and vending machines are selling gold, with younger people flocking to buy. Bite-sized gold bars have been selling since April, weighing in between 0.1 and 1.87 grams.

One gold buyer who spent $30,000 on the precious metal this year called Costco's offerings a "gateway drug" into gold investing.

While not a typical outlet for the sale of precious metals, the members-only warehouse chain has seen its 1-ounce gold bars sell out faster than discounted 170-ounce jugs of laundry detergent.