Match the pattern’s stitch gauge before starting a fitted project. If you count too many stitches across the stated span, try a larger hook; if you count too few, try a smaller one. Then make and measure another swatch. Hook size is a starting setting, not proof of fit.
Measure a useful swatch
Use the intended yarn, the specified stitch pattern and the same flat or in-the-round method as the project. Make the swatch larger than the measuring area so edges do not distort the count. Follow the pattern’s blocked or unblocked instructions; if it gives finished washed gauge, wash and dry the swatch as you will care for the finished piece.
Lay it flat without stretching it into the required size. Count both stitches and rows through the middle. Use the exact span stated: 4 inches is 10.16 cm, so do not silently substitute 10 cm when checking a tight fit.
Gauge and repeat calculator
Crochet gauge and repeat calculator
Compare your blocked swatch with the pattern, then see neighboring repeat-compatible counts for your target size.
Example values are loaded. Replace them with your measurements. Your entries stay in this page.
Use the calculator to see your result.
The calculator compares stitch counts over entered spans and offers whole repeat counts. It does not rewrite a garment pattern or decide whether an altered size will fit.
For example, 20 stitches per 10 cm gives two stitches per centimeter. A 30 cm rectangle needs 60 stitches before any edge allowance. If the stitch pattern requires a multiple of eight, 56 stitches gives 28 cm and 64 gives 32 cm. Neither is exactly 30 cm. Add any separately required edge stitches according to the pattern.
If you instead make 25 stitches per 10 cm, those same 60 stitches produce 24 cm: 20% narrower than intended. These are arithmetic examples, not measured yarn tests.
When only one gauge matches
Changing hook size can change both width and height. If stitch gauge matches but row gauge does not, check that you are forming the specified stitch and measuring the intended fabric. Work-to-length directions may accommodate a different row count, but armholes, increases, decreases and colorwork can require coordinated changes. Ask the designer or use a pattern-specific adjustment rather than simply adding rows everywhere.
Also judge the fabric. A substitution that reaches the count but becomes too stiff, open or heavy is not necessarily suitable. The yarn selection guide covers the separate fiber and care checks. Once the yarn is suitable, use the skein calculator for quantity.
Blankets and scarves still change size and yarn use when gauge changes. Their fit may be less critical, but measuring first helps avoid an unexpectedly narrow blanket or an extra yarn purchase.