Primal Play runs in eight sizes, the same ladder across boxer briefs and undies:
2T · 3T · 4T · 5T · 5/6 · 7/8 · 10/12 · 14/16
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 encased waistband has a good deal of give, so 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.