How to Make a Soft Mattress Firmer: Your Step-by-Step Guide

Do you prefer firm mattresses, but have somehow ended up sleeping on a mattress far too soft? Learn how to make a mattress firmer in 7 steps.

By Nicole Gleichmann

Aug 15th, 2022

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Sinking too far into a mattress is a sure-fire way to get a poor night’s sleep. Whether your new mattress is softer than you expected or an old one is becoming a bit too snuggly with age, there are ways to up a mattress’s support. Can you make a mattress more firm without buying a new one? Follow these 7 steps if you’re ready to make your bed firmer.

7 Tips to Make Your Mattress More Firm

Step 1: Check Your Warranty or Trial Period

Do you have a new mattress that isn’t what you hoped it would be? Or an older mattress that is beginning to sag too much? If you fall into either of these categories, you might have the option to return your mattress or cash in on its warranty. This can save you time and money and potentially offer a long-term solution.

When buying a new mattress, you will find that many mattress companies offer a trial period. During the first 30 or 100 days, you may be able to return or exchange the mattress at little to no cost to you. Every company is different. If you find that you are unhappy with a new mattress, contact the company to see what your options are.

For those of you who have an older mattress that is showing signs of wear and tear, determine if it is still under warranty. If so, research to see if what you’re experiencing would qualify you for a replacement or rebate.

Step 2: Flip or Rotate Your Mattress

Every mattress should be flipped or rotated every 3 to 6 months. Flipping a mattress only works for those that are built with two sleep surfaces. The simple act of flipping your mattress can provide immediate support and extend the bed’s longevity.

Rotating the mattress is an option whether or not you can flip your mattress. By rotating the mattress, you sleep on portions of the surface that you have not recently compressed with your body weight.

If your mattress is able to be flipped, flip it once every 6 months and rotate it once every 3 months. The idea is to sleep on as much of the bed’s surface as possible. This will result in less sagging and sinking, allowing you to sleep more comfortably.

Step 3: Turn Down the Temperature

Depending on your type of mattress, it may become firmer when the temperature is cooler. Memory foam beds are the most impacted by room temperature. Turning down the thermostat, opening a window, or using a fan can make a memory foam bed much firmer. You may notice slight differences with other mattresses as well.

Step 4: Dry Your Mattress in the Sun

For anyone who lives in a humid environment, you may find that your bed firms up when you allow it to air dry in the sun. When kept indoors, your mattress can accumulate moisture from the air, making it softer over time. Another benefit of airing it out in direct sunlight is that you will kill off mold and bacteria that’s lurking inside.

Step 5: Use Taut Bedding

This trick is best used for people with pillow top mattresses, a mattress type best suited for side sleepers. These mattresses have an incredibly soft and luxurious upper layer. While this can feel great right when you lie on it, it may not offer enough support. Particularly for back and stomach sleepers.

Replace your fitted sheet with a large flat sheet or comforter. Pull the sheet or blanket taut and tuck it around the entire perimeter. This can pack down the down or other pillow top materials to create a firmer sleeping surface.

Step 6: Check Your Mattress’s Foundation

What foundation are you using for your mattress? If it is a box spring or slatted foundation, there are ways that you can boost your mattress’s support, and with it, the support that your mattress gives you.

Box springs are made from metal coils that provide some give. Over time, box springs can weaken, offering less support. Replacing a box spring can make your mattress feel firmer. And if this is not enough, or if you do not want to buy a new box spring, a sheet of plywood can be inserted between the box spring and the mattress to offer additional support.

Similarly, you can make a slatted foundation more supportive by inserting a sheet of plywood between the bed frame and the mattress. Keep in mind that using plywood boards can void some warranties. If you do use this option, cut the plywood to match the exact dimensions of the mattress. Sand down the corners and edges to reduce the risk of getting a bruise or splinter if you bump into it.

Another way to ensure that your mattress is solidly supported is by placing it directly on the floor. The floor is the hardest foundation available, and as such, can help make your mattress feel firmer. But keep in mind that having your mattress on the floor puts you in close contact with dust, bugs, and other allergens.

Step 7: Buy a Mattress Topper

Using a firm mattress topper is typically the most effective thing that you can do to make a current mattress feel firmer. Dense memory foam or latex foam mattress toppers that measure greater than two inches can even out a lumpy or saggy surface and make an overly soft mattress more supportive.

For a mattress that is sinking in, you may need to add blankets, pillows, or something else to even out the surface before you place the topper. And if your mattress is aging and quite saggy or soft, you may not find a topper to offer sufficient support.

Word of warning—do not mix up a mattress pad for a mattress topper. Mattress pads are thin sheets of padding made from soft materials like cotton, wool, or polyester. These products will usually make mattresses softer.

When It’s Time to Buy a New Mattress

Getting a good night’s sleep is important. When a mattress is too soft, it can result in aches and pains and nights spent tossing and turning. Rather than spend time and money trying to fix your existing mattress, you may find that you are better served buying a new mattress that is the right firmness level for you. Particularly if you are trying to squeeze some extra time out of an old mattress. Make sure to read our guides on the best firm mattresses and best mattresses that don’t sag for recommendations, or our best beds of 2023 guide for a broader variety of options.

If you do choose to buy a new mattress, choose a mattress with a trial period that allows you to ensure that it’s the right mattress for you.