Measure and mark the new hem length before you cut

Put on the slacks with the shoes you plan to wear them with, and stand in front of a mirror. The hem should break slightly on the top of your shoe — not pooling on the floor, not riding above your ankle. Have someone mark that line with tailor's chalk or a fabric pencil while you stand still, or do it yourself by pinching the fabric where it should end and marking both legs at the same height.

Take off the slacks and lay them flat on a table. Measure from the mark down to the original hem edge. Add one inch to that number — that extra inch is what you'll fold under and stitch. For example, if you marked 2 inches up from the old hem, you'll cut 3 inches up from the old hem. Mark a straight line all the way around both legs at that distance, using a ruler and tailor's chalk or fabric pencil.

Try the slacks on one more time to confirm the mark is level and at the right length. Uneven hems are the most visible mistake, so take the extra minute here.

Key Takeaways

  • Mark the new hem length while wearing the slacks with the shoes you'll wear them with, then add one inch for the fold-under before you cut.
  • Cut off the old hem and the excess fabric in a straight line, then fold the raw edge under by half an inch and press it flat with an iron.
  • Fold that pressed edge up again to create a half-inch hem, press it, and pin it every two inches before sewing.
  • Use a straight stitch on your machine with matching thread, sewing slowly and removing pins as you reach them.
  • Press the finished hem with an iron to set the stitch and remove any puckering.

Cut the old hem away and press the new fold

Cut along the line you marked, removing the old hem and the excess fabric. Use sharp fabric scissors and cut as straight as possible — a crooked cut will show in the finished hem. Discard the cut-off piece.

Fold the raw edge of the fabric under by half an inch and press it flat with a hot iron. This fold prevents fraying and creates a clean edge inside the pant leg. Let it cool for a few seconds so the crease sets.

Fold that pressed edge up again by another half inch, so you now have a half-inch-wide hem folded in half. Press this fold as well. The raw edge is now hidden inside the fold, and you have a crisp crease to sew along.

Pin the hem every two inches before sewing

Place pins perpendicular to the fold, spacing them about two inches apart all the way around the pant leg. The pins should go through all the layers and hold the fold in place without bunching the fabric. Start at a seam so your stitching line is less visible.

Check that the hem is still level by holding the pant leg up to the light or laying it flat and eyeing the fold. Uneven pinning creates an uneven hem, so adjust as needed before you sit down at the machine.

Sew the hem with a straight stitch, removing pins as you go

Thread your machine with thread that matches the slacks as closely as possible. Set the machine to a straight stitch with a stitch length of 2.0 to 2.5 millimeters — this is a standard length for hemming and creates a strong, invisible seam. Use a new needle if you have one; a dull needle can skip stitches or snag the fabric.

Start sewing at a seam, about a quarter inch from the fold. Sew slowly and steadily, keeping the fold aligned with the presser foot. Remove each pin just before the presser foot reaches it — do not sew over pins, as this can break the needle or damage the machine. Backstitch at the start and end to lock the thread.

Sew all the way around the pant leg, keeping the stitches as close to the fold as possible. The stitches should be small enough that they do not show from the outside of the pant leg, but large enough to be strong. If you sew too close to the very edge of the fold, the stitches may pop out with wear.

Press the finished hem to set the stitch

Turn the pant leg inside out and lay it flat on an ironing board. Press the hem with a hot iron, using firm pressure to set the stitches and remove any puckering or wrinkles. Let it cool before you move it.

Turn the pant leg right-side out and press the outside of the hem as well. This final press makes the hem lie flat and gives the slacks a finished look. If you see any puckering or loose threads, trim them with small scissors.

Repeat the process for the second pant leg

Measure, mark, cut, press, pin, and sew the second leg using the same steps. The key is to make both hems the same length and the same width so they look matched. If the first leg took you 20 minutes, the second will go faster because you now know the rhythm.

Once both legs are hemmed and pressed, try the slacks on to confirm the length is even and the hem sits where you want it. If one leg is slightly longer or shorter, you can unpick a few stitches, adjust the fold, and re-sew that section. Hemming is forgiving — mistakes can be fixed.

Frequently Asked Questions

What thread color should I use?

Match the thread to the slacks as closely as possible. If the slacks are black, use black thread; if they are navy, use navy. If you cannot find an exact match, choose a shade slightly darker rather than lighter — darker thread is less visible in a hem. You can also use thread that matches the inside of the pant leg if it differs from the outside.

Can I hem slacks without an iron?

An iron makes the job much easier and creates a crisper, more even hem, but you can fold and pin without one. The hem will be less precise and may wrinkle more easily, but it will still hold if you sew it securely. Press the fold flat with your fingers and let it sit for a few minutes before pinning.

What if the hem puckers while I'm sewing?

Puckering usually means the fabric is bunching under the presser foot. Slow down, keep gentle tension on the fabric in front of and behind the presser foot, and make sure the fold is lying flat. If puckering happens, unpick that section, re-press the fold, and sew again more slowly.

How do I fix a crooked hem?

Unpick the stitches with a seam ripper, working slowly to avoid tearing the fabric. Re-press the fold, re-pin it at the correct height, and sew again. It is easier to fix a crooked hem right away than to live with it, so do not hesitate to redo a section that does not look right.

Should I use a special presser foot for hemming?

A standard presser foot works fine for hemming slacks. Some machines have a walking foot or a roller foot that can help prevent puckering on slippery fabrics, but these are not necessary for most cotton or wool slacks. Stick with what came with your machine unless you run into problems.