A correctly tensioned stitch looks the same from both sides, with the two threads locking in the middle of the fabric layers rather than on either surface.
The test that makes it obvious. Thread the top in one colour and the bobbin in a strongly contrasting one, then sew a straight seam on a doubled scrap of your actual fabric. Now look at both sides.
- Bobbin colour visible on the top surface → top tension is too tight.
- Top colour visible on the underside → top tension is too loose, or the thread is not in the tension discs.
- Neither colour crossing to the other side → correct.
This takes two minutes and it removes all the guesswork. Most people adjust tension by feel and by eye on matching thread, where the fault is invisible until the garment is finished.
Adjust in half-numbers, sewing a test seam after each change, and only ever the top tension. The bobbin is factory-set. If the top dial cannot bring the stitch into balance across its whole range, the problem is not tension — go back and check threading, needle and bobbin class.
Re-test whenever you change fabric weight. A tension that is right for quilting cotton is often slightly tight for silk and slightly loose for denim.
Questions people actually ask
Should I adjust tension for every fabric?
Check it for every noticeably different fabric, and adjust if the test shows an imbalance. Most machines cope with a range of ordinary wovens on one setting.
What number should the dial be on?
There is no universal answer, and a machine that needs an unusual setting to balance is telling you something else is wrong. Judge by the stitch, not by the number.
Last reviewed 2026-08-11