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How to Measure a Mattress Sag for a Warranty?

When it comes to ensuring a good night’s sleep, your mattress plays a pivotal role. However, over time, even the best mattresses can develop sagging, leading to discomfort and potential sleep disturbances. This is where understanding how to measure a mattress sag for a warranty becomes crucial.

In this post, we’ll walk you through the step-by-step process of evaluating your mattress’s sag, providing you with the knowledge needed to make informed warranty claims. So, let’s delve into the details and equip you with the tools to enjoy a comfortable and restful sleep.

Table of Contents

Common Types of Mattress Sag

Here are different types of mattress sag.

  • Center Sag
Center Sag in the mattress

If you sleep primarily on the center of your mattress repeatedly, that part of the mattress is mainly likely to sink. This is because your hips and shoulders lie at the center and exert pressure.

If the bed is still under warranty and you have noticed a sag, it can be repaired or replaced after measuring it and adhering to warranty guidelines.

Center sag can also be due to poor-quality materials used in the construction of the mattress. The materials will sag after sleeping at the center repeatedly for a short period.

  • Edge Sag

The edge support usually supports most heavy people. While it mainly prevents them from falling, most people typically sleep on the edge of a mattress repeatedly. It, in turn, can make the edge area sag prematurely.

Also, depending on the materials used to construct the mattress, your edge might stay firmer, longer, or shorter. Poor quality of materials used for designing a bed can make an edge sag prematurely when used repeatedly with heavier or overweight people.

  • Body Impression

Body impression is the compression and settling of the fiber, foams, and fabrics within the upholstery layers of your mattress. You will notice body impressions in the mattress areas where the body weight puts pressure on these layers.

Most soft and plush mattresses usually show body impressions after a short period of use. It is because its fillings are loose hence settling and compression occur quickly.

How to Measure Mattress Sag: Step by Step

Here is a step-by-step process to successfully measure the sag for warranty. Have a look.

1. Gathering All the Tools

You will need the following set of tools:

  • Yardstick/broom, string – To assist with measuring the dip
  • Measuring tape – To measure the depth of the mattress sag (you can use any measuring tape, but a steel measuring tape is preferable)
  • Ruler – To take measurements of the width.
  • Camera – To capture pictures of the mattress sag for warranty claims.
  • Painters tape – To secure things in place (only use it if you opt for a string)

2. Strip off All the Bedding

Strip off all your bedding from the mattress, including pads, toppers, and sheets, to accurately measure the depth. 

Please remember you do not want your results to be altered or to make the measuring process difficult. The best way to achieve this is to remove any bedding from your mattress.

It’s vital to note that if you have laid on a memory foam recently, you will have to give it a few hours to decompress before you can proceed with taking measurements. This enables it to gain its natural state so that the measurements can be accurate.

3. Prepare to Measure the Depth

You need to place a yardstick or broom specifically across the mattress width for it to reach the deepest layer of the depression. 

Alternatively, if you opt for a string, please secure one end to the mattress edge using painter’s tape and slowly pull the string taut towards the dip. Then fix it using tape on the other side of your bed.

Painter’s tape is usually a great option because it doesn’t leave any residue on your mattress fabric after removing it.

4. Measure the Mattress's Depth

Measure the Mattress's Depth

When your broom (or yardstick) and string are well set over the depression in the mattress, you can begin measuring the dip.

Measure the dip beginning from the string towards the mattress. Remember, when using stiff measurement devices like steel measuring tape or ruler, practice caution and not place excess pressure onto the mattress to avoid exaggerating the depth.

To archive excellent measurements, you should ensure only the tip of your measuring tape rests gently on the mattress surface.

Then check the zone where the depth shows the lowest point and measure from that area to the bottom of your string, yardstick, or broom. By doing this, you will know the depth of the impression on your mattress.

5. Interpret Your Findings

If you notice the distance of the depression is more than 1.5 inches, it implies that the mattress body impression is not within the recommended body impression depth and vice versa. You can go ahead and place your claim.

What Is Not Covered Under a Mattress Warranty?

It’s vital to note that your mattress warranty might not cover anything physically defective or physically flawed. Below are things that a mattress warranty might not cover.

  • Discoloration and stains
  • Dissatisfaction
  • Normal wear and tear
  • The mattress owner performed damage.

Factors Affecting Measurement Accuracy

Several factors affect your mattress’s measurement accuracy; they are as follows.

  • Mattress Type and Materials
mattress types

Memory foam mattresses tend to compress when slept on. The materials used to construct the bed are soft and plush foam. If you take measurements immediately after using the mattress, you may not get the correct measurement.

It will help if you give the bed a few hours to decompress to its original state before you proceed with your measurements.

  • Body Weight Variations

Your body weight determines the amount of pressure your mattress will get. If you place pets, babies, or other things on your bed frequently, they may put pressure on their placement areas, which will make your mattress have different kinds of sags.

  • Environmental Conditions

Fluctuating temperatures can negatively influence the accuracy of your measurements. In our case, we need very accurate measurements.

The warmer the environment around your house gets, it may cause the expansion of some materials in the mattress hence affecting the measurement accuracy. 

During the cold seasons, excess moisture may access the mattress, causing it to sag or reduce in size, altering the measurements.


Can I measure mattress sag with a regular tape measure?

While a regular tape measure can be used, a flexible, tailor’s measuring tape is recommended for more accurate results.

What if my measurements are slightly below the warranty requirement?

It’s best to reach out to the manufacturer’s customer support and discuss the situation. They might still be able to assist you.

Is mattress sagging preventable?

While sagging is inevitable with use, rotating your mattress regularly can help prolong its lifespan and delay the onset of sagging.

Do mattress toppers affect sag measurements?

Yes, mattress toppers can impact measurements. It’s best to remove the topper before measuring sag.

How often should I measure mattress sag?

It’s a good practice to measure sag every six months to a year, especially if you notice changes in comfort or support.

What is the acceptable sag depth for a warranty claim?

Warranty guidelines vary, but a sag depth of around 1.5 inch or more is often considered significant enough to warrant a replacement.

Can a mattress topper fix sagging?

While a mattress topper can provide temporary relief, it won’t address the underlying sagging issue. It’s best to address sagging directly with the manufacturer.

Is sagging covered by all mattress warranties?

Not necessarily. It’s important to review the specific terms of your mattress warranty to understand what types of sagging are covered.

Are there preventive measures against mattress sag?

Yes, using a high-quality, supportive foundation and rotating your mattress periodically can help minimize the risk of sagging.

Should I replace my mattress if it sags?

If your mattress sags and it’s still under warranty, it’s advisable to explore the warranty claim process before considering a replacement.


Getting accurate mattress measurements is crucial when you want to claim a warranty. You have to measure the mattress gently and accurately. You can use a string, yardstick or broom alongside a measuring tape to successfully measure the sag.

Remember, different types of mattress sags will guide you when taking measurements. These include edge sag, center sag, and body impression.

Author: Jessica

Jessica is a lover of both life and gardening. She loves to share his passion for both on social media. He often posts about his latest gardening projects, as well as tips and tricks for others who might be interested in starting their own gardens. She also frequently posts about the different aspects of his life that he enjoys, from spending time with friends and family to exploring new places.

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