The picture below provides an indication of the change in size of an article when crocheted using the same pattern, but using different thread sizes (with the appropriate size hook as above). Using a finer thread results in a smaller but more finely textured article. Depending on the pattern, some articles may be crocheted in a wide variety of sizes while others go out of shape or do not sit flat if a different size thread is used.
The chart below provides an approximation only of how to determine the finished size of an article crocheted in a thread size other than that specified. Please note that this only works for some patterns and is a rough guide only.
Using the column with the specified thread size, go down until you locate the red 1, then go across to the column with the thread size you wish to use. Multiply the figure shown by the specified size of the article to provide the new finished size.
Example: Assume a doily was crocheted using #60 thread with a finished size of 20cm in diameter and you wished to use #20 thread. Go to the #60 column and run down to the red 1. Now go across to the #20 column and the figure is 1.4. Multiply the original size of 20cm by 1.4 and the finished size should be about 28cm.
| Thread #10 | Thread #20 | Thread #40 | Thread #60 |
| 1 | 0.85 | 0.7 | 0.6 |
| 1.2 | 1 | 0.8 | 0.7 |
| 1.45 | 1.25 | 1 | 0.9 |
| 1.65 | 1.4 | 1.15 | 1 |