How to Measure Your Bed for a Custom Mattress
You need four numbers: width, length, depth, and the shape of anything that is not a rectangle. Measure the frame opening, not the old mattress, and measure in millimetres if you can.
Take the old mattress out first
Every measurement below is of the space the mattress will sit in, not of the thing currently sitting in it. Old mattresses bow outward at the sides, compress at the corners and sag in the middle. Measuring one and ordering to that number is the single most common reason a custom mattress arrives wrong.
Width and length
Measure the clear internal opening — rail to rail, and headboard to footboard.
- Take the width at the head, the middle and the foot. Use the smallest of the three.
- Take the length down both sides. Use the smaller one.
- Work in millimetres. "1348" is a measurement; "about 135" is a guess.
- Measure twice, on different days if the frame is old timber. Wood moves.
Do not subtract anything for clearance. Tell us the opening and we will apply the tolerance — a mattress needs to be slightly under the opening, and how much under depends on the cover and the fillings, which is our job to know.
Depth
Depth is a choice, not a measurement, but two things constrain it.
- The surround. Measure from the slat surface to the top edge of the side rail. A mattress much shallower than the surround feels like sleeping in a box; much deeper and you lose the edge support the frame was giving you.
- Safety rails. On a bunk or a child's cabin bed, the rail must stand at least 16 cm above the sleeping surface once the mattress is in. That usually caps the mattress at 15 cm on a bunk. This is the reason our SlimFit exists at 16 cm.
Shapes that are not rectangles
Draw it. A photograph of a pencil sketch with numbers on it is worth more than a paragraph of description.
Cut corner
Give us the two legs of the triangle — how far in along the head, and how far down along the side — and say which corner, viewed from standing at the foot of the bed looking towards the pillows.
Radiused corner
Find a round object that matches the curve, measure its diameter and halve it. A dinner plate is about 130 mm radius, a mug about 40 mm.
Tapered or boat berth
Give us the width at the head, the width at the foot, and the length. If the taper is not symmetrical, say so and mark which side is which.
Sloping wall or attic
Measure the height of the wall at the point the mattress edge will meet it, and how far the slope cuts in at mattress height. An attic bed usually needs a cut corner along the full length rather than at one corner.
Check the frame is square
Measure both diagonals of the opening. If they differ by more than about 10 mm, the frame is a parallelogram, not a rectangle. Tell us the diagonals as well as the sides and we will cut to the actual shape. If you do not, a mattress cut square will bind on two corners and gap at the other two.
What to send us
- Width at the narrowest point, in mm.
- Length at the shortest point, in mm.
- Depth you want, in cm.
- A photo of a sketch, if anything is not a plain rectangle.
Everything except the sketch goes straight into the configurator, which prices it as you type and draws the cut sheet so you can see what you are ordering before you commit.
Common questions
Can you work from imperial measurements?
Yes, but convert once and tell us the millimetres. Fractions of an inch get lost in translation and the factory works in millimetres.
What if I measure wrong?
A made-to-measure mattress is cut for one bed and cannot be resold, so it falls outside the 100-night trial. That is exactly why we would rather you spent ten minutes with a tape than five. If you are unsure, send the numbers and the photo and we will check them before anything is cut.