The number of coils in a mattress varies from product to product and is based on a queen-size mattress. If there is only one number listed, it is the amount of coils in a queen size and the number for other sizes is proportionally higher or lower. The number of coils in a particular system is important in determining the quality of the innerspring mattress, but it is not the only attribute you should consider. Coils design, quality and their arrangement are also critical. As a general rule, more coils of the same design and the same gauge equal better support and better durability. But sometimes with increased number of coils their size and their thickness decrease, thus providing softer support.
Make sure you are comparing the coil count of the same system in the same size (it's a good practice to compare numbers in queen size), as mentioned above, individually pocketed coil system will often have more coils than continuous coil system. The coil count of various products can vary form under 400 to over 1000 in queen size. As a rule of thumb, you shouldn’t consider a mattress for an adult with less than 600 coils in queen size.