Apple usually announces a new iPhone in September, so it’s not too early to start thinking about your old iPhone.

It has some value. In fact, it may be worth a lot more than you think, even if it is scratched and has a broken screen. You might be able to get over $100 for such a beat-up phone. But the value of the smartphone seems to depend as much on what carrier you use as how much storage (or memory) it has.

You can sell old iPhones — a lot of Android phones, too — to a number of online companies. Gazelle.com, cashforiphones.com, usell.com and icracked.com are just a few of them. Amazon and eBay are also vibrant marketplaces for used iPhones. I don’t know which one offers the best price or which are the most reputable. I don’t have enough used iPhones to do comparison testing.

But looking at the prices offered for the used iPhone 5s may offer some insight into what phone to buy next if you intend to sell it after a few years of use.

Before going on, may I just stop and say I am not suggesting you buy a new phone. Use the phone you have as long as you can, as you would a car or a refrigerator. There are few good reasons to replace a phone every year or two.

O.K., now on to the observations. First, the phone’s color doesn’t seem to matter a whit.

Memory does matter, but not the way you might think. It makes sense to buy a phone with as much memory as you can afford, since it soon becomes packed with memory-hogging apps, magazines, emails, messages and photos. But if you think in terms of resale, you get the best return on a phone with the smallest amount of memory.

Apple sells its base 16 gigabyte 5s phone for $200 and then doubles the memory and bumps the price up $100. But the additional memory does nothing for the resale value, according to a number of resale sites. (I used data from gazelle.com as a representative example.) Your best return is the base 16GB memory phone, but in every case the value of the 64 GB phone drops.

What matters most is the carrier providing the service. Verizon iPhones have the best resale value. A 16GB phone can actually be worth 62.5 percent more than you paid for it (if you bought your phone with a contract). An AT&T phone does almost as well; its 16GB phone can be worth 40 percent more. (All values were computed using an undinged phone.)

Sad, sad Sprint. A phone on that carrier loses value in all cases.

The phones retain and even gain value because they can be sold to people in the United States where Verizon and AT&T are the most popular networks, or overseas where the phones are compatible with a country’s system of cell towers.

Cracked screens can be replaced and light scratches buffed out. But remember, if you monogrammed your phone or had your name printed on it, sorry. No one, anywhere, thinks it is cool to own that phone.

 
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