Method
We model the hat as a tapered cylinder: area ≈ circumference × depth × 0.85, then apply yarn density and 10% waste. Use finished hat circumference (often 1–2" negative ease for knit ribbed hats).
Worked example
Adult 22" × 8" depth, worsted knit: expect roughly one 200 yd skein with leftover for a pom-pom.
Tips
Measure above the ears. For double-brim hats, increase depth before calculating.
Common mistakes
Skipping negative ease for stretchy knits; underestimating faux-fur pom yarn.
Sizing guidance
Preemie hats may be 10–12" around; baby 14–16"; toddler 18–20"; adult small 21"; adult large 23". Depth includes brim. For a folded brim, add the fold height to depth before estimating yarn. Slouch adds 1–3" of depth and noticeable yardage. Fur pom-poms are usually purchased separately; yarn pom-poms may take 20–40 yards.
Limits and how to use the results
Estimates run only in your browser. Prefer a published pattern’s tested yardage when it conflicts with this planner. Density factors and assumptions are documented on the methodology page; legal terms cover planning-use limits.
FAQ
How much yarn for an adult hat?
About 100–180 yards of worsted for a classic beanie; bulky may need only 60–100 yards.
Child hat yardage?
Try 18–20" circumference and 6–7" depth for many toddlers.