How To Measure a Mattress Size: Simple Steps and Common Questions

If you’re wondering how to measure a mattress size—whether for a new bed frame, bedding, or to identify what size you already own—you’re in the right place. This guide explains the basics of mattress measurements, how to measure accurately, and what details most people overlook.

What Does “Mattress Size” Actually Mean?

When people talk about mattress size, they’re usually referring to three measurements:

• Length (head to toe)
• Width (side to side)
• Height/Thickness (top to bottom)

Most standard mattress names (like twin, full, queen, king) are based on length and width. Height can vary widely, even within the same size category.

Knowing how to measure a mattress size helps you:

• Match it to a bed frame or base
• Choose the right sheets and mattress protectors
• Understand if it will fit in your room or through doorways

How To Measure a Mattress Size Step by Step

1. Prepare the Mattress

Before measuring:

• Remove all bedding: sheets, blankets, toppers, and pads
• Make sure the mattress is lying flat on a firm surface
• If possible, slide it away from walls so you can access all sides

This helps you get more accurate measurements and avoid including pillows or toppers by mistake.

2. Measure the Width

Use a tape measure:

1. Stand at the side of the mattress.
2. Place the tape at the widest point on one edge.
3. Extend it straight across to the opposite side.

Record the result in inches or centimeters. This is your mattress width.

3. Measure the Length

Next:

1. Move to the head or foot of the bed.
2. Place the tape at the very top edge of the mattress.
3. Run it straight down to the bottom edge.

This number is your mattress length.

4. Measure the Height (Thickness)

To measure thickness:

1. Place the end of the tape on the floor or bed base (whichever the mattress rests on).
2. Measure vertically up to the highest point of the mattress surface.

Avoid pressing down on the mattress while measuring, as this can make it seem thinner than it really is. Mattress height often ranges from low-profile (around 5–8 inches) to extra-thick designs.

How Do My Measurements Compare to Standard Mattress Sizes?

Once you know your mattress’s length and width, compare them to common standard sizes. Actual measurements can vary slightly by manufacturer, so it’s normal to be off by an inch or so.

If your measurements are very close to one of these, that’s likely your mattress size.

Frequently Asked Questions About Measuring Mattress Size

Do I measure the mattress or the bed frame?

When you’re focused on how to measure a mattress size, measure only the mattress, not the frame or foundation. Frames and headboards can be a few inches larger than the mattress, which can cause confusion.

If you’re buying sheets or a protector, mattress measurements are what matter. If you’re checking fit for a frame, it can be helpful to measure both the mattress and the inside dimensions of the frame.

Should I include the mattress topper?

To know true mattress size, measure only the mattress. Toppers can be added or removed and may change thickness. However, if you’re buying fitted sheets and always use a topper, you may want to record:

• Mattress thickness alone
• Mattress + topper thickness

This helps you choose fitted sheets with the right pocket depth.

What if my mattress doesn’t match any standard size?

Some mattresses are custom, antique, or non-standard. If your measurements don’t align well with standard sizes:

• Double-check with a second measurement
• Note all three dimensions clearly
• Look for bedding labeled as “deep pocket” or “oversized” if your mattress is unusually thick

Non-standard sizes may need special-order bedding or flexible options like adjustable strap sheet sets.

How precise do I need to be?

For most purposes, measuring to the nearest inch is enough. If you’re working with a particularly tight frame or custom bedding, you may want to be more precise, especially with width.

Tips for Accurate Mattress Measurements

• Use a soft measuring tape (like one for sewing) if available; it curves easily along edges.
• Measure twice to confirm your numbers match.
• Measure from edge to edge, not including rounded corners beyond the usable sleep surface.
• If the mattress has a pillow top, include it in the height, as it affects sheet fit.

✅ Quick Mattress Takeaways

Key points consumers should understand about How To Measure a Mattress Size:

• Always measure three dimensions: width, length, and height.
• Remove all bedding before you measure to avoid inaccurate results.
• Measure just the mattress, not the frame or headboard.
• Compare your numbers to common mattress size charts to identify your size.
• Height (thickness) matters for choosing fitted sheets and protectors.
• Slight size variations are normal between different mattress makers.
• If your mattress is non-standard, write down exact measurements and use them whenever you shop for bedding or accessories.

Understanding how to measure a mattress size takes only a few minutes and can prevent a lot of frustration with ill-fitting frames, sheets, or accessories. With clear measurements in hand, it’s much easier to choose items that match your mattress and your space.