My back started hurting every morning, and I blamed my mattress. It was seven years old and sagging in the middle. I priced new mattresses and nearly fell over. Then a friend suggested trying a mattress topper first. It was the cheapest fix for my back I have ever found.

Here is what I learned shopping for a topper under 100 dollars.

Know your sleep position first

Back sleepers need firm support with a little cushion. Side sleepers need more pressure relief at the shoulder and hip, which means a softer topper. Stomach sleepers need the firmest option, because a soft bed sinks the lower back. Buy for your position, not for the trendiest material.

Memory foam vs latex

Two main options in this price range. Memory foam is soft, molds to your body, and is great for side sleepers and pressure relief. The downside: it sleeps hot, and the cheap ones can feel like a marshmallow that swallows you. Latex is firmer, bouncier, and cooler, which suits back and stomach sleepers. Under 100 dollars you mostly get memory foam, and the decent ones work fine.

Check the density, not just the thickness

A thick, squishy topper looks great in the listing but might be low-density foam that flattens out in a month. Look for the density number in the specs. Something around 3 to 4 pounds per cubic foot is a good middle ground for a budget topper. If the listing does not say the density, assume it is low and move on.

What I bought and how it went

I got a 3-inch memory foam topper with a cooling gel layer for around 80 dollars. The first night felt like sleeping on a new mattress. The cooling layer actually helps, which surprised me, because budget memory foam usually sleeps hot. After six months it has held its shape and my morning back pain is mostly gone. It is not a magic cure, but it took the edge off exactly where I needed it.

One honest warning

A topper cannot fix a truly broken mattress. If your mattress is sagging so deep that you roll into the middle at night, no topper will save it. A topper is for a mattress that is firm but uncomfortable, not one that is structurally done. If the middle sags more than an inch or two, save the 80 dollars toward a new mattress.

For me, the topper bought two or three years of good sleep on an old mattress, for a fraction of the cost of a replacement. If your back hurts in the morning and your mattress is not completely shot, try the topper first.