Hem Measurement: How to Measure Width, Length, and Allowance

A hem measurement can describe a garment’s bottom width or circumference, its finished length, or the fabric allowance folded up inside. For sewing and alterations, establish where the finished hem should fall before measuring the allowance or cutting fabric. Keeping those measurements separate is the key to getting the right length without accidentally trimming away the fabric you need.

What Hem Measurement Means

Before measuring, identify which measurement you actually need:

Hem width: The distance across the bottom of a garment laid flat. On pants, this usually means the opening of one leg.
Hem circumference: The distance all the way around the bottom opening.
Finished length: The distance from a defined starting point, such as the shoulder or waistband, to the finished bottom edge.
Hemline: The line where the finished bottom edge will fall. On a turned hem, this is the main fold.
Hem depth: The width of the finished turn-up on the inside of the garment.
Hem allowance: All the fabric extending below the intended hemline before folding.

Hem depth and allowance are not always identical. If you turn the raw edge under before folding up the hem, that extra tuck must be included in the allowance.

For an online clothing listing, “hem measurement” usually concerns the bottom opening. For an alteration, it usually concerns the finished length and the allowance needed to achieve it.

How to Measure and Mark an Even Hem

Gather a flexible measuring tape, a ruler or sewing gauge, fabric-safe chalk, pins, basting thread, scissors, and an iron suitable for your fabric. A helper makes marking a worn garment much easier.

Step 1: Prepare the Garment Before Measuring

Complete the fitting and construction first. On a new garment, finish everything that affects how it hangs, leaving the hem unfinished. Let it hang for 24 hours on a cushioned hanger before marking, especially when a substantial part is cut on the bias, according to New Mexico State University Extension. Bias-cut fabric can settle unevenly, changing the bottom edge.
Release an existing hem when altering it. Remove the old stitching and press out the crease. If you are lengthening the garment, inspect the exposed fabric for fading, wear, or a permanent crease before deciding how much length you can recover.
Address likely shrinkage before an alteration. For a washable garment, use its intended laundering method before taking the final measurements. Do not stretch the fabric while pressing or handling it.

Step 2: Choose the Hem Depth and Calculate the Allowance

Use these general hem-depth ranges as a starting point, then confirm the intended finish in your sewing pattern and account for the garment type, edge flare, and fabric weight.

Garment or Edge Shape	Common Finished Hem Depth
Skirts, dresses, and coats	2 to 3 inches (5 to 7.5 cm)
Jackets, pants, and blouses	1 to 2 inches (2.5 to 5 cm)
Straight edges	2 to 3 inches (5 to 7.5 cm)
Flared or circular edges	Use a narrower hem depth for flared or circular edges.

Read the garment and edge-shape rows together. These are overlapping guidelines, not amounts to add. A circular skirt may need a narrower hem than the general skirt range because a deep turn-up creates more fullness to accommodate.
Choose the edge finish. An overcast raw edge needs no additional tuck. A double-fold hem needs enough allowance for both the finished depth and the raw-edge turn-under. Very bulky fabric may work better with a lighter-weight hem facing.
Calculate the full allowance before cutting. Cut length = desired finished length + total hem allowance.

The cut length is longer than the finished length by the total hem allowance. Measure both lengths from the same starting point.

Step 3: Mark the Finished Hemline

A level hem comes from a settled, fitted garment, not simply an equal turn-up from its raw edge.

Put the garment on as it will be worn. Wear the intended undergarments and shoes, position the waistband normally, and stand on a level floor. Look straight ahead rather than bending to inspect the hem.
Establish the intended bottom edge. Have a helper fold or mark the fabric at the desired length. For a level skirt or dress hem, measure vertically from the floor to that point, then maintain that floor-to-hem distance around the garment.
Make the initial reference marks. Establish the hemline at 4–6 points around the garment, using seams and spaces between them. With the garment off, mark the chosen hem depth or allowance from those reference points, then pin between the marks.
Connect the hemline marks smoothly. Support the fabric without stretching it. Keep the finished hemline and the cutting line clearly distinguishable.

Do not assume that equal measurements down from a waistband will produce a level hem. The way fabric passes over the body affects where the bottom edge falls.

Step 4: Baste, Check, and Then Trim

Fold along the marked hemline. Place pins at right angles to the edge every 2 to 3 inches (5 to 7.5 cm), then baste close to the fold.
Try the garment on again. Check the front, back, and sides while standing naturally. If the length or balance is wrong, release the affected basting, adjust the fold, and baste again.
Measure the allowance before trimming. Take the garment off and turn it wrong side out. Measure from the approved fold toward the raw edge, mark the required allowance, and trim only the surplus hem fabric. Keep the garment body clear of the scissors.

Cutting comes after the fitting check. An uneven raw edge can be corrected; an allowance cut too short is much harder to recover.

Step 5: Finish a Basic Turned Hem

For a straightforward hand-sewn hem on a stable woven fabric:

Finish the raw edge. Overcast it, or turn it under by the amount included in your allowance.
Re-form the main fold. Press without stretching, using an iron setting appropriate for the fabric, and baste the hem in place.
Hand sew the upper edge. Alternate a small stitch in the hem allowance with a tiny catch of the garment fabric. Keep the thread relaxed enough that it does not pull the outside into dimples.
Finish and inspect. Secure the thread ends, remove the basting, and give the hem a final press. Try on the garment and check that the finished edge hangs smoothly.

Hem Measurement for Different Garments

Hem measurement varies by garment: assess dresses, skirts, pants, jeans, blouses, and shirts as worn while preserving intended curves or asymmetry.

Dresses and Skirts

A straight, level hem is judged on the body, not by whether every panel has the same length on a table. Bust, hip, and seat shaping can change how much fabric is needed at different positions.

Before shortening an uneven skirt, check its shortest section. The finished line must leave enough fabric there for the chosen allowance unless you plan to add a facing or another deliberate extension.

Keep an intentional high-low or asymmetric design intact. Such a hem should follow its intended shape rather than being forced parallel to the floor.

Pants and Jeans

Check both legs independently. Matching their lengths while laid flat does not guarantee that they will hang identically when worn.

The desired break, the fold where the front of the pant leg meets the shoe, also affects the finished length. A tailored trouser hem may sit differently at the front and back, so equal floor clearance around each opening is not always the goal.

Cuffs and original-hem alterations need their own construction allowance. A plain turned-hem calculation does not automatically provide enough fabric for them.

Blouses and Shirts

For a blouse intended to hang level, assess the bottom edge while it is worn or on a correctly fitted dress form. Matching side-seam lengths alone will not account for the way the front passes over the bust or the back falls over the body.

Slippery, loosely woven, and bias-cut panels can also hang differently after assembly. Support the fabric while marking instead of pulling it flat.

A curved shirttail is different: its front, back, and sides are intentionally different lengths. Preserve the curve and measure the allowance inward from that curve rather than trying to level it to the floor.

Curved hems, hems with binding or lace, narrow topstitched knit hems, and machine-sewn blind hems solve different construction problems. Start each with a fitted garment, an approved hemline, and enough fabric for the chosen allowance.

Curved Hems

A curved hem’s raw edge is often longer than the garment area it must lie against after folding. Ease that extra length rather than pressing it into pleats.

Trim to the selected allowance and overcast the raw edge if the fabric ravels.
Sew an easing line 1/4 inch (6 mm) from the cut edge. Leave the thread ends accessible.
Fold along the marked hemline. Gently draw up the easing thread and distribute the fullness until the allowance lies smoothly, without visible gathers.
Baste and press without flattening tucks into the garment.
Hand sew the upper edge with small, relaxed catches into the garment fabric. Secure the thread, remove temporary basting or exposed easing stitches, and press again. Check the outside for puckering.

If the allowance will not lie flat without gathers, the hem may be too deep for the curve.

Hems With Binding or Lace

Seam binding or suitable stretch lace can cover a raw hem edge without adding the bulk of another fabric fold.

Mark the hemline, check the length, and trim to the intended allowance.
Place the binding or lace on the right side of the hem allowance, overlapping the cut edge by 1/4 inch (6 mm). Stitch through the overlap to attach it, keeping the tape relaxed. Overlap and secure its ends.
Turn the hem to the wrong side along the marked line, press, and baste.
Hand sew the free binding or lace edge to the garment with tiny catches that do not show prominently outside.
Secure the thread ends, remove basting, and press. Check that neither the tape nor the stitching pulls the garment inward.

Narrow Topstitched Knit Hems

A narrow topstitched finish suits soft knits and fabrics that do not ravel.

After marking and checking the hemline, trim the allowance to 5/8 inch (1.5 cm).
Turn the allowance to the wrong side along the hemline. Press and baste without stretching the fabric.
With the right side facing up, topstitch 1/2 inch (1.3 cm) and 3/8 inch (1 cm) from the folded bottom edge. If the opening needs to stretch, use a stretch-capable stitch rather than a tight straight stitch.
Secure the thread ends, remove the basting, and press without dragging the iron. Gently stretch the opening as it will stretch during wear, checking that the stitches hold and the edge lies flat.

Test the stitch on a scrap of the same fabric before sewing the garment. A stretched-out sample signals that the fabric needs better support or a machine adjustment before you continue.

A blind hem leaves very little stitching visible on the outside.

Finish the raw edge, turn up the approved allowance, press, and baste. On fine fabrics, the raw edge can be turned under; on medium- to heavyweight fabrics, overcasting avoids an extra fold.
Set up the machine. In SINGER’s blind-hem method for its sewing machines, the setup uses a Blind Stitch Foot with thread tension set to Auto, selecting Regular Blind Stitch for normal firm fabrics or Elastic Blind Stitch for soft, stretchable fabrics. Confirm the corresponding stitch symbol, compatible foot, and available tension control in your model’s manual; not every machine has an Auto setting.
Fold the garment body back over the turned-up hem so the finished allowance edge extends beyond the fold. With the wrong side facing up, place it under the foot so the straight stitches land on the allowance and the sideways stitch barely catches the garment fold.
Turn the handwheel toward you to check the needle’s sideways movement. Adjust the guide so the needle just catches the fold, then test the arrangement on matching scrap fabric.
Sew slowly, keeping the fold against the guide. Secure the thread ends, unfold the garment body, remove basting, and press. Inspect the right side: large visible bites mean the needle caught too much fabric.

Check the Finished Hem

Inspect the garment from both sides and while it is worn:

Length: The garment falls where intended with the appropriate shoes.
Shape: A level hem looks level; a shaped hem retains its intended curve.
Allowance: The inside edge lies flat without bulky ridges or accidental pleats.
Stitching: The seam is secure, with no skipped stitches, puckering, or pulled spots.
Movement: The opening allows the movement or stretch the garment needs.
Finish: Temporary pins and basting are removed, and loose thread ends are secured.

If something looks wrong, release the affected stitching and correct the fold or tension rather than trimming more fabric immediately. Once the hem is right, record the finished length, allowance, and finishing method with your pattern notes.

Frequently Asked Questions

How Do I Calculate Hem Circumference?

Hem circumference is the distance around the entire bottom opening. For a simple, straight hem with equal front and back widths, double the laid-flat width to estimate the circumference. For curved, pleated, asymmetric, or unevenly shaped openings, measure along the entire finished edge with a flexible tape without stretching the fabric.

How Do I Measure a Hem When I’m Alone?

Use a stable, adjustable hem marker while wearing the garment, or mark it on a dress form that closely matches your measurements. Set the marker to the desired floor-to-hem height and make marks while standing upright rather than bending toward the edge. Remove the garment, connect the marks, baste the fold, and check it in a full-length mirror before cutting. If you cannot assess the back clearly or the dress form fits differently, have a helper verify the line before you trim.

How Do I Measure the Length of a Shirt?

Lay the shirt flat without stretching it and measure from the high shoulder point, where the shoulder meets the neckline, down to the finished bottom edge. Another common measurement is center-back length, taken from the back neckline seam to the back hem, excluding the collar. Label which method you used, and record front and back lengths separately when the shirt has a curved or high-low hem.