Formula
stitches = round(width_in × (1 + ease%/100) × (stitchesPer4in / 4) × ribbingFactor). A ribbing factor near 0.9 helps when casting on in rib that springs in.
Worked example
20" width, 20 sts/4" (5 sts/in), 5% ease → 21" effective × 5 = 105 stitches.
Tips
Round to your rib multiple. For hats, use negative ease (−10% to −15%).
Common mistakes
Using unblocked gauge; forgetting pattern multiples.
Multiples and edge stitches
After calculating a raw cast-on, adjust up or down to the nearest pattern multiple (for example, a multiple of 4 + 2 for 2×2 rib). Add selvage stitches if your pattern’s gauge rectangle excludes them. Long-tail cast-on yarn length is roughly 1 inch per stitch for worsted—estimate separately from fabric yarn needs.
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.
Choosing a cast-on method
Long-tail cast-on is elastic and common for ribbed edges; cable cast-on is firmer for bags and structured hems; tubular cast-on blends into 1×1 rib. The stitch count from this calculator is independent of method, but long-tail requires estimating tail length separately—about three times the finished width for many worsted projects. If you use a needle one size larger for cast-on, your edge may flare; re-check width after a few rows.
FAQ
How many stitches to cast on for a hat?
Use head circumference with negative ease and your stitch gauge.
What is ease?
Ease is the difference between body and garment measurements.