Diaper Size Guide: Get the Fit Right, End the Leaks

Nine out of ten leak complaints we see are a fit issue. Diapers are sized by weight, not age — here is the chart we use.

The chart

• NB: up to 4 kg
• S: 4–8 kg
• M: 7–12 kg
• L: 9–14 kg
• XL: 12–17 kg
• XXL: 15+ kg

The two-finger test

You should be able to slide two fingers under the waistband. Red marks on thighs mean size up. Gaps at the leg cuffs mean size down.

Overnight is different

For 10–12 hour stretches, use a dedicated overnight diaper one size up from daytime. The extra core absorbs 2–3 more wettings.

Browse our Diapering range — every product page lists the weight band.