What is truing and why do I need it?

Truing a pattern is the process of checking and correcting seams, darts and hems on a pattern which not only makes a pattern easier to sew, it also reflects right through to the fit and hang of the garment. It is a small, yet very important part of patternmaking and a useful skill for all sewers.

Presumably, commercial patterns have been trued by the designer, but it doesn't hurt to check. Personal alterations to a pattern can distort the outline and the pattern must be re-trued before being cut. Dress Shop patterns are custom drafted to individual measurements and produces a slightly different pattern shape for each person. This makes it difficult to produce perfectly trued seams and darts for everyone so take a few minutes after taping the pattern together to check and true your pattern before cutting. It will help tremendously when sewing the garment together and give you pucker free garments and smooth, even hems.

Most seams intersect with either another seam, a hem or other finished edge and these intersecting edges must flow in a smooth line either for appearance, fit or ease of sewing. For example: If the shoulder/armhole intersection is not smoothed or trued, you will find the sleeve puckers right at that shoulder point and does not hang nicely. A similar thing happens on a side bust dart if the dart cap is not jogged out correctly. The inside fold of the dart can be caught too tightly in the seam making the fabric bubble out at the side seam just below the dart.

You cannot true patterns pieces individually; corresponding seamlines must be butted against each other and corrected together. The term 'true' implies making it at a right angle but on patterns, it is more important that the angles either side of the seam complement each other and that the adjoining seams flow in a smooth curve.

General tips:

  • Check the pieces in the order in which they are sewn together to methodically catch every spot.
  • Always match the stitching lines when truing.
  • Do not trim the excess paper off your pattern until you true that seam, as you frequently need extra paper beyond the cutting line.
  • On Dress Shop patterns, the seam allowances occasionally vary in width in certain areas. Redraw the seam allowance as needed. NOTE: The Stitching line is always correct; The Cutting line should be redrawn if it is uneven.


Decide in which direction the dart will be pressed on the finished garment. Fold the dart leg closest to that direction in an upward crease. Put your fingernail at the end of the dart point. Pinch the creased dart leg and pivot it over to the matching dart leg. Flatten the dart while the remainder of the pattern cups upwards. You could also fold the dart over the square corner of a table. In this case, allow the pattern to cup downwards over the table corner as you pivot and flatten the dart. It is sometimes easier to redraw the seam lines with this method but it can be tricky to fold exactly to the dart point. 

While the dart is folded, true the stitching and cutting lines, trace through all layers with a tracing wheel and if possible also cut along the cutting line to get the correct dart cap shaping.

Fold dart and true seam line
(no seam allowances shown)
Click for larger image
Side bust dart trued for folding down.
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Side bust dart trued for folding upwards.
Note the different dart cap.
Click for larger image


A frequent alteration is shortening or lengthening a pattern piece. On angled or curved seams this produces a jog on the seamline. Blending is smoothing out the line so it looks like a scaled version of the original. This is done on individual pieces.

If it is a straight line, re-draw it from the start to end point. If you don't want to lose fullness,e.g.: on a side seam in the bust region, create a gentle curve over the jog.
For curved lines (e.g. sleeve cap), start the blending at a comfortable distance away so the new line flows smoothly and imitates the original. Skim off the high side and add to the low side of the jog usually crossing the jog in the center (example a). In some cases you don't want to lose any fullness, so blend from the high side, over the jog and onto the low side line (example b).

Fold dart and true seam line
(no seam allowances shown)
Click for larger image

Check seam length and intersecting lines
Fold under the seam allowance on the one pattern piece. Lay the pieces alongside each other and overlap the seam allowances. Match the stitching lines of both pieces aligning the ends. Check the seam lengths, taking into account darts and gathers, and adjust if necessary.

Smooth the intersecting seam lines adding or skimming to get a suitable smooth curve. Keep in mind the shape of the piece that will join onto this seam (e.g.: collar onto the neckline). Add or trim the jogs on the seam allowances.

True intersecting seamlines at armhole
(no seam allowances shown)
Click for larger image
True intersecting neck seamlines
(no seam allowances shown)
Click for larger image

Curved seams - Walking a pattern to check length 
This term is used to describe when a curved piece is incrementally matched against a straight or less curved piece in order to check that the seam lengths match (e.g.: on a collar and neckline) or how much ease is allowed (e.g.: a sleeve into an armhole). It is important that the stitch/seam line of the two pieces is matched - not the cutting line. Curved seams can be walked with pieces directly on top of each other (sleeve and armhole) or alongside each other with seam allowances overlapping (front princess panel line)

Match the patterns at the end of the seamline (A) and as far as possible along the seam to (B). Place a pin or ballpoint pen at (B) on the stitching line to secure the patterns. Pivot the top pattern piece at (B) until the next section of seamline matches as far as possible to (C). Move the pin to (C) and pivot until (D). Continue all the way around until the end of the seam. The sharper the curve is, the shorter the matched sections should be. Re-mark notches and intersecting seams along the curves as you walk the pieces. If a piece does not match well, walk it in the reverse direction to double check or find the problem area. Remember you are measuring and comparing the stitching line not the cutting line.

The other advantage of walking a pattern is so you can compare the shape of the curves at important locations.

True intersecting seamlines at armhole
Click for larger image

Curved seams - Measuring to check length 
Hold a tape measure on edge and follow the curve of the pattern on the stitching line . Write down the measurement at notches and intersections so you can compare to the corresponding piece/s.

Tapered and princess seams
Sharply tapered seams such as godets and armhole princess seams can create long extensions from seam allowances. A good rule of thumb is to trim them across the point to the width of the seam allowance you are using. Mark the intersecting point of the seamlines and match that when sewing.

Sleeves frequently have a tapered seam which meets the hem at a wide angle. The hem allowance needs to jog out to match the seam when it is folded. Fold the hem and trace the seam angle onto the hem allowance.

If the sleeve seam is sharply tapered, fold the sleeve into a tube and overlap the seams. Fill in the V formed by the hemline and remark the hem width. This will create a slightly curved hemline. Fold the hem at the ends to create the jog. The new hem cut line will have a slight bias edge which should stretch sufficiently for the hem turn up. This works best with hems less than 3cm wide. If you need the hem wider and it is significantly curved consider using a separate hem facing.

True hemlines
Click for larger image


The hemline on skirts and blouses must first be trued into a smooth line across the side seams. This will reduce the need for harsh jogs. The hem allowance is then adjusted evenly. Flared skirt hems are not trued with a jog. The excess curve length is taken up with easing.

Example sequence for truing patterns


  • Fold the back shoulder dart. Redraw the shoulder seam and cut. The dart cap extension is automatically cut at the correct angle. Mark notches at the seam line for the dart legs.
  • Overlap the bodice at the shoulder seams. Match the back to the front shoulder and check for equal length seams.
  • At the neckline, fill in any excessive scoop on the back neck, meeting at the neck point and slightly scoop the side of the front neck. Imagine this as a finished neckline or having to sew a collar on to this neckline. You don't want severe dips or points.
  • At the shoulder point smooth the armhole across the shoulder seam. Sketch a smooth stitching line starting from about 8 cm (3") either side of the shoulder point, adding on a small amount (3 - 5 mm / ") at the shoulder point. This will give you a tiny bit more shoulder width than you measured. If you don't want to add this tiny bit, scoop off inside the armhole curve from the shoulder point and blending in at the across chest or across back position.
  • Fold the side bust dart and true the side seam creating the correct dart cap shape.
  • Match the front and back side seams from the underarm point down. Check and balance the side length at the waist edge. Add to the front side length if necessary.
  • Check the armhole curve at the underarm is smooth.
  • Check the waistline flows in a smooth curve from front to back across the side seam. Fold the waist darts and smooth the remaining waistline from the side seam to center. Remember the center line creates a mirror image so that should be smoothed to perpendicular.


  • Fold elbow dart and true.
  • Walk the sleeve into the bodice armhole. Confirm sufficient cap ease.
  • True sleeve hem.

Skirt or pants:

  • Overlap side seams together at waist portion. If the side seam is curved, match for about 5 -10 cm ( 2- 4") down the side seam. True the waist seam. Fold the waist darts or pleats and blend the waistline.
  • If a skirt is joined to the bodice for a dress, match the skirt waistline to the bodice waistline and true the lengths.
  • Check the length of the side seams and blend the hem. For skirts blend the hem over a larger distance. Watch that the side seams will not droop lower than the center when the garment is worn. If the side seam is very biased and the fabric is likely to stretch on the bias grain, trim the excess off at the side seam. The hem will hang straight when worn.
  • On pants, match  the inleg seams at the ankle / hem and smooth the hem.
  • The inleg seam of pants should match equally from hem to knee notch. From knee to crotch point, the back inleg may be equal or up to 1.3 cm (1/2") shorter than the front inleg depending on fabrics and pant style. This allows the back inleg seam (which is more biased and likely to sag later) to be stretched to fit the front inleg giving a better fit to the pants back.
  • Match the inleg seams at the crotch point and ensure the crotch curve makes a smooth 'U' shape.

Copyright by Tessa Elston, 2004, 2005.
All content, descriptions, drawings and presentation style are copyrighted by Tessa Elston and may not be reproduced or imitated.

Created October, 2004
Last updated 23rd November, 2004