What are grade rules?

Grade rules describe how the base size steps up and down through a size range, written as a base measurement plus a step. The base is the approved starting point. The step is the agreed change applied to a particular measurement or pattern location. Different points can have different rules.

The useful idea is BASE + STEP, not “make the whole garment bigger”. A shirt needs its bust, shoulder, sleeve and length relationships to remain deliberate across the range. A grading chart records those decisions so the pattern grader and factory are not left to choose them from a single sample.

Begin with an approved base

A rule cannot correct an unresolved base garment. Before grading, check the base-size fit, measurements and construction. If the waist seam sits too high in the base size, applying a size step will repeat that decision across the range. Establish which version is approved and which measurements the chart takes as its starting point.

Name the base size and complete size range. Size names are labels, not a universal set of dimensions. A factory cannot derive your intended customer or fit from the letter on a sample alone. The base chart and agreed fit direction need to describe the starting garment clearly.

A step belongs to a defined measurement

On a finished-measurement chart, a grade step describes the change between stated sizes at a particular point of measure. A bust-width rule is connected to the measuring method for bust width. If that method is a flat width, the step must use the same basis rather than silently switching to full circumference.

For illustration only, a flat width of 50 cm with a 2 cm step would become 52 cm in the next size up and 48 cm in the next size down. Those are arithmetic examples, not recommended shirt measurements. The appropriate base and steps depend on the intended fit and size range.

A row should make the unit, direction and size interval clear. A value that means “per adjacent size” must not be applied once across two intervals. State any departure from a regular interval instead of expecting the reader to infer it from the names at the top of the chart.

Read the grading chart across and down

Across a row, the chart shows how one measurement changes through the size range. Down a column, it describes the relationship between measurements within one size. Both views matter. A row can progress neatly while the resulting shoulder, sleeve and bust proportions no longer work together.

Use the same point identifiers and methods as the base-size spec. A reference on the diagram should lead to the correct row without interpretation. For more on the measuring side, see what a garment spec sheet is. The grading chart extends the agreed method rather than creating a separate one.

Review the smallest and largest sizes as well as the base. A rule that seems minor near the middle can produce a noticeable difference after several steps. The chart should make those end values visible enough to check, not hide them behind an unexplained formula.

Not every point grows by the same amount

Width, length and detail positions do not necessarily increase together. A collar point may remain the same while neckline dimensions change. Button spacing, cuff proportions and peplum depth need their own decisions. Applying one percentage to every line would alter details that may be intended to stay constant.

Some ranges also require different steps in different intervals. Write those changes where they occur and check the resulting proportions. Do not assume that repeating a single step is correct simply because it is easy to calculate. The chart should record the intended fit system, not substitute arithmetic convenience for a decision.

Measurement rules and pattern movement are related

A finished-measurement step describes a result on the sewn garment. A pattern grade rule describes movement at a defined pattern point, often in horizontal and vertical directions. The two are related, but one is not a direct copy of the other. Seams, shaping and the distribution of growth affect how pattern movement produces a finished measurement.

For example, a change to a full garment width is distributed across relevant pattern areas, not added in full to every side seam. Matching seams also need to remain compatible. The grader checks those relationships while applying the rules, rather than moving every outline outward by the same distance.

The general process is covered in what pattern grading is. This guide concerns the written rules that make the intended changes explicit, so they can be checked and applied consistently.

Grade rules are not a full graded pattern set

A chart of measurements and steps does not contain the complete cutting shapes for every size. A full graded pattern set is a separate output. It includes the pattern pieces needed for the agreed range, with their relevant information and matching relationships. Do not treat a column of size measurements as proof that those files are supplied.

When asking a factory or technical designer for grading, name the output you need. Ask whether the scope includes written grade rules, a base-size pattern, a full graded set, or a combination. Clear scope prevents a pack from being described as incomplete when a different deliverable was expected.

Review changes before issuing the chart

If the approved base changes, revisit the grading chart. A new base measurement combined with old steps may still be suitable, but it needs checking. Record the revision and make sure the factory knows which version to use. Separate sample corrections from changes intended to affect the whole range.

A useful final check is to read each row aloud as a rule: this point, this method, this base, this change between these sizes. If a part of that sentence is missing, the chart is not yet explicit enough. The aim is a size range that follows agreed decisions, not a set of plausible-looking numbers.