This Guide should help you find the correct size when buying a new pair of Levi's Shrink-To-Fit 501 Jeans:
The famous Levi's Shrink-To-Fit 501 jeans are made with the UNSHRUNK DENIM that hasn't been washed and the shrinkage process will be complete only after the initial washing. In other words when you buy a new pair of Shrink-To-Fit 501 jeans - they will shrink considerably after you wash them the first time! This is also true for all other RIGID and UNSHRUNK denim garments, such as jackets, vests, shirts, skirts etc. Any alterations on a new pair of unshrunk jeans (including the leg length alterations) are not recommended until shrinkage is complete. Please note that the shrinkage rate might vary slightly between garments, especially with Vintage and Vintage Reproduction garments.
If you want to determine what size to get when buying the NEW & UNSHRUNK 501 Shrink-To-Fit Levi's jeans you need to look at the Levi's Shrinkage Guide (which is conveniently listed on oneeuroman's "About Me" page). There you'll find the tables which will help you determine the correct size for you so that the jeans you buy will fit you properly after the shrinkage process is complete.
You'll find that the LABELED SIZE doesn't necessarily correspond to the actual measurements of a new pair of jeans. This is especially true with the unshrunk 501 jeans. For example a brand new pair of the Shrink-To-Fit 501s with the LABELED Size W34 L36 might have the ACTUAL Measurements W36 L36 or W35 L37 etc. It's all hand made, after all :) so when looking for the correct size for you - YOU NEED TO LOOK at the ACTUAL MEASUREMENTS.
The first and most important step is to determine what jeans size fits you:
To do so you can either use the measure tape and measure your own waist and inseam, or you can measure the waist and inseam on your favorite pair of 501 jeans. When taking the measurements from your favorite pair of 501s make sure you lay them on a flat surface and avoid stretching the denim.
Here's an example for a buyer that normally wears jeans in size 34 x 34 (again the Actual Measurements, not the Labeled Size):
First we need to look at the Shrinkage Guide (listed on oneeuroman's "About Me" page) and find the Waist size in the left column (in this case waist size of 34 inches) and then look at the number on the right under the "Increase Size By" column: 1 inch. This gives us the ACTUAL Waist size of 35 inches (34 + 1 = 35 inches).
Now we look for the Inseam size in the left column (in this case inseam size of 34 inches) and then we look at the number in the right column: 3 inches. This gives us the ACTUAL Inseam size of 37 inches (34 + 3 =37 inches).
Now we are ready to look for the Shrink-To-Fit 501 jeans with the ACTUAL Size of W35 L37 that will shrink down to W34 L34 after being washed.
Some people prefer not to wash their jeans in order to maintain the original rigid feel and look. This is sometimes recommended by Levi's for certain RIGID jeans other than the 501s. You will often find the washing instructions on the inside tag of the Rigid jeans that might look like this: "Rigid garments require special care. To maintain Rigid look - dry cleaning is recommended. Home laundering could cause shrinkage up to one size". In this case the only way to maintain the original size of the UNSHRUNK or RIGID Denim Garments and avoid the shrinkage process is to have the jeans DRY CLEANED.