One-page diaper fit checklist

Run these checks on the exact pack in your hand, using your baby's current weight in kilograms, before a large order and at the first few changes.

Use your browser's Print option to keep a paper copy or save it as a PDF. The page is laid out to print on one sheet.

Before you buy

Weigh your baby this week; diaper sizes follow weight, not age.
Find that weight inside the range printed on this exact pack, not on a chart from another brand or an older order.
Pant and tape versions of the same letter can carry different ranges; check the one you are buying.
Between two sizes? Start with the smaller one, in the smallest pack available.

At the change: waist

Waistband level around the tummy, just below the navel.
One finger slides inside comfortably; no digging in, no rolling down.
Pants: pulled fully up so the absorbent centre sits snug, back edge a little higher than the front.
Tapes: both fastened at the same height, landing on the front panel rather than stretching to its edge.

At the change: legs

Both leg frills turned outward; run a finger round each thigh.
Openings rest against the thigh with no visible gap and no deep pressing.
A fresh, correctly positioned diaper that still gaps is too big or the wrong shape; a larger size will not close the gap.

After a few hours

A faint line at the waist or thigh that fades within a minute is normal.
A red mark that is still there at the next change is not.
Watch your baby kick, crawl or curl up: the waistband stays level and the leg openings stay closed.

Time to move up when you see these together

Red marks on the waist or thighs that last until the next change.
Tapes at the outer edge of the front panel, or a pant waistband that looks stretched and sits low.
Leaks that repeat while the diaper is not full, as your baby nears the top of the range.
One leak on one night is not a size signal.

If it leaks at night

Note where the wetness is before you strip the bed: hip or thigh, back waist, front waist, or soaked everywhere.
Hip or thigh: turn both frills out; if a fresh diaper still gaps, the size or shape is wrong, not too small.
Back waist: pull pants fully up; fasten tapes higher and evenly.
Front waist: keep the front panel high; point a boy downward at the change.
Soaked everywhere: a fresh diaper just before your own bedtime, then compare absorbency; a bigger size is not the fix.
Change one thing at a time and keep a note for a few nights.

Read the full guides

The checklist is a summary. The reasoning behind each item is in the diaper size guide, the overnight leak guide and the pant style vs tape guide.

Weight ranges differ between brands and between pant and tape products, so use the range on the exact pack you are buying; this checklist is general guidance, not medical advice.