How do I measure cot bar spacing and mattress-to-rail height on a used cot?

How do I measure the gap between cot bars?

Use a rigid tape or a ruler, not a soft dressmaker’s tape that bows. Measure the clear gap between two neighbouring bars — inside edge to inside edge — at several heights, and keep the widest reading. Do this on more than one side of the cot. This section is the method only; the published centimetre figures sit in the table below, each with its own source.

1. 1
   Assemble the cot as the instructions show NCT says read the assembly instructions; they are usually online if the paper copy is missing. A half-built side will give a false gap.
2. 2
   Pick three pairs of bars One near a corner, one in the middle of a long side, one on the other long side.
3. 3
   Measure inside edge to inside edge Hold the tape square. Record millimetres if your tape shows them, then convert (10mm = 1cm) so you can compare with each source.
4. 4
   Repeat at mattress height and near the top rail Bars can bow. Keep the largest gap you find.
5. 5
   Write the number next to the source you will compare Do not average NCT’s 6cm with Which?’s 6.5cm. Note both.

How do I measure mattress-to-rail height?

Put in the mattress you will actually use — a thinner spare changes the reading. Measure from the top face of the mattress straight up to the top of the lowest side rail. NCT also publishes a second figure that includes the mattress thickness; write that down separately rather than mixing the two.

1. Fit the mattress so it sits as it will for sleep. NCT wants no more than two fingers’ width between mattress and cot side; Which? says there should not be a gap of more than 3cm.
2. Measure mattress-top to rail-top on both long sides. Keep the smaller height if they differ.
3. If the base is height-adjustable, measure again on the position you will use when the baby can pull to stand. Which? says the lowest base is the one the instructions usually treat as the later position.
4. Record mattress-top-to-rail and, if you follow NCT’s second line, rail height including the mattress.

What figures do NCT, Which?, the NHS and RoSPA publish?

UK pages do not all print the same centimetres. This table quotes each range with its source. MayTally does not choose a 'correct' number or turn your tape reading into a pass mark.

If two sources print different centimetres, write both numbers in your notes. Do not average NCT’s 6cm with the 6.5cm figure on the Which? and NHS pages.

Why does RoSPA want vertical bars, not a ladder?

RoSPA says cots with bars on all four sides can let air circulate, and that the bars should be vertical. If they are horizontal, RoSPA says a baby could use them as a ladder to climb out. NCT’s used-cot list also asks for vertical bars. Horizontal decorative slats on an heirloom cot are therefore a RoSPA / NCT observation to record, not something this page grades.

Just One Norfolk NHS says if a second-hand cot is old or a family heirloom, make sure it would pass today’s standards, and to buy a new mattress conforming to BS EN 16890. The NHS and NHS Start for Life prefer a new mattress; Which? says buy a new mattress for a second-hand cot and keep the mattress-to-frame gap to no more than 3cm.

In shortMeasure the widest bar gap and the mattress-top-to-rail height with the mattress in. Write NCT’s 6cm / 50cm (and 60cm including mattress) next to Which? and NHS 6.5cm and Which?’s 2.5–6.5cm / 50cm, and note RoSPA’s vertical-bar line. Quote the source. Do not pick a winner or write a safety score.