Primal Play runs in eight sizes, the same ladder across undies and boxer briefs:
2T · 3T · 4T · 5T · 5/6 · 7/8 · 10/12 · 14/16
How to measure
Lay a pair that already fits your child flat and compare. These are garment measurements, not body measurements.
If your child is between sizes, size up.
The measurements below are for boxer briefs.
Toddler (2T-5T)
| Size | Age (guide) | 1/2 waist | 1/2 hip | Side length | 1/2 leg opening |
|---|---|---|---|---|---|
| 2T | 2 | 7.5 in (19 cm) | 9.8 in (24.8 cm) | 6.7 in (17 cm) | 4.8 in (12.3 cm) |
| 3T | 3 | 7.9 in (20 cm) | 10.2 in (26 cm) | 7.1 in (18 cm) | 5.0 in (12.8 cm) |
| 4T | 4 | 8.3 in (21 cm) | 10.9 in (27.8 cm) | 7.7 in (19.5 cm) | 5.3 in (13.55 cm) |
| 5T | 5 | 8.7 in (22 cm) | 11.7 in (29.6 cm) | 8.3 in (21 cm) | 5.6 in (14.3 cm) |
Toddler and kids sizes use different patterns. The kids block is cut slimmer through the hip and leg, and longer in the rise — so 5/6 is not simply larger than 5T in every measurement.
Kids (5/6-14/16)
| Size | Age (guide) | 1/2 waist | 1/2 hip | Side length | 1/2 leg opening |
|---|---|---|---|---|---|
| 5/6 | 5-6 | 8.9 in (22.5 cm) | 11.5 in (29.25 cm) | 8.5 in (21.5 cm) | 5.5 in (14 cm) |
| 7/8 | 7-8 | 9.7 in (24.75 cm) | 12.5 in (31.8 cm) | 9.1 in (23 cm) | 6.0 in (15.25 cm) |
| 10/12 | 10-12 | 10.8 in (27.5 cm) | 13.8 in (35 cm) | 9.8 in (25 cm) | 6.6 in (16.75 cm) |
| 14/16 | 14-16 | 12.4 in (31.5 cm) | 15.4 in (39.1 cm) | 10.6 in (27 cm) | 7.4 in (18.75 cm) |
Age is a guide only. The measurements are the authority.
Undies share the same size ladder, but the pattern differs and we have not finished measuring it. Detailed undies measurements are coming, and will be published here. Until then, use the guidance above and size up if you are between sizes.
Which one to pick
The toddler sizes, 2T through 5T, are cut with a higher rise and a shorter leg, sized for a child who may still be in the middle of potty training. The numeric sizes, 5/6 through 14/16, follow standard kids' apparel sizing.
Note that 5T and 5/6 overlap. If your child is five, 5T has the higher rise and 5/6 has the longer body. Go by which they prefer rather than by age.
If you are between sizes
Size up. The waistband is soft fabric with no separate elastic tape or strip, so it has some give and a slightly larger size sits loose rather than gapping, while a slightly small one is the thing most likely to be rejected outright. This is the single most common adjustment parents tell us about.
How they should fit
The waistband should sit flat, with no rolling. The leg opening on the boxer brief should rest against the thigh without gripping it. If there is still a visible line after an hour of wear, go up a size.
After washing
Wash cold and tumble low and these will hold their size. Hot water and high dryer heat will shrink any cellulose knit, so avoid both.
Still unsure
Email us with your child's age and the size they wear now, and we will tell you what we would send.