Size Grading for OEM Clothing: What Brands Need to Prepare Before Bulk Production

Fit errors are one of the most expensive problems in bulk apparel production — and most of them start before the factory cuts a single piece of fabric. When a brand's size specifications are incomplete or inconsistent, the factory interprets the gaps, the pre-production samples come back wrong, and the back-and-forth begins. By the time the issue surfaces in bulk, the cost in time, shipping, and remake fees is high.

The root cause, in most cases, is not a manufacturing error. It is an incomplete or misread size submission. This guide covers what brands need to prepare on the sizing and grading side before placing an OEM order — what to include, how to verify it at the sample stage, and where the common mistakes happen.

What Size Grading Means in OEM Clothing Production

Size grading is the process of adjusting a base pattern up and down across your full size range. It is not a uniform scale-up — each point of measure (POM) on the garment follows its own increment rule, and those rules are set by the brand, not the factory.

In OEM production, grading becomes a practical handoff document. The factory receives your base size sample and your graded spec sheet, then produces all other sizes by following the increment rules you have defined. If those rules are missing, unclear, or inconsistent across measurement points, the factory will either ask for clarification (which adds lead time) or make a judgment call (which adds risk).

The base size is typically the size from which your first sample is developed — most commonly a Medium for adult tops, or whatever size your fit model represents. All other sizes in your range are derived from this base. Confirming the base size explicitly in your tech pack prevents a common source of confusion when factories assume a different starting point.

Industry Standards vs Brand-Specific Grade Rules

ASTM publishes standardized sizing tables for various apparel categories, and some factories default to these when a brand does not provide its own grade rules. However, ASTM standards are developed for broad market reference, not for any individual brand's fit intent. Relying on factory defaults often produces a size run that is technically proportional but does not match your brand's fit positioning — especially for categories like activewear or fitted silhouettes where small measurement differences have a visible effect on how the garment performs.

For reference on standardized measurement categories, see ASTM Textile Standards — though your brand's own grade rules should always take precedence in OEM submissions.

What Your Size Chart Must Include Before Sending to a Factory

A consumer-facing size chart — the kind that shows body measurements alongside size labels — is not what a factory needs. What the factory needs is a garment measurement specification: the actual dimensions of the finished garment at each point of measure, across every size in your range.

These two documents serve different purposes, and submitting the wrong one is one of the most common errors brands make in their first OEM engagement.

Key Elements of a Factory-Ready Size Spec

Element	What to Include	Common Gap
POM List	Every measurement point labelled consistently (e.g., chest at 1" below armhole)	Vague labels like 'chest' without measurement position
Measurement Method	Flat or circumference; half or full — stated explicitly for each POM	Inconsistent method between POMs causes factory confusion
Grade Increments	The size-to-size increment for each POM across the full size run	Missing increments; factory defaults to uniform grade
Tolerances	Acceptable + / - deviation per POM (e.g., ±0.5 cm on chest)	No tolerance stated — factory cannot know what is acceptable
Base Size Label	Clearly mark which size is the base (the sample size)	Factory assumes a different base and grades from the wrong starting point

The table above covers the minimum required components. Any POM that appears in your spec without a grade increment or tolerance will be filled in by the factory's judgment — which may or may not match your brand's intent.

Connection to Your Tech Pack

Your size spec is not a standalone document — it is a core section of your tech pack. Factories that work with proper OEM workflows expect to receive size specifications as part of a complete tech pack submission, not as a separate spreadsheet sent after sampling has begun.

For a full breakdown of what a tech pack should contain before submission, see clothing tech pack requirements for OEM production.

How to Verify Grading Accuracy at the Pre-Production Sample Stage

Approving a single sample in your base size does not confirm that grading has been applied correctly. Grading errors only become visible when you measure across the size range — and if you catch them at the pre-production sample stage, corrections are still straightforward. Catching them after bulk cutting is a different situation entirely.

Size Set Samples vs Single-Size Samples

A size set sample is a pre-production run that includes one unit from each size in your range, produced using the graded spec. Requesting a size set before approving bulk production is a recommended checkpoint for brands ordering across more than two sizes. Reviewing only the base size sample tells you whether the fit is correct in that one size — it tells you nothing about whether the grading increments have been correctly applied to the rest of the range.

For brands ordering custom t-shirts or similar cut-and-sew pieces, the size set review should focus on chest, body length, and sleeve length as the three highest-impact POMs. For stretch categories such as gym leggings or activewear bottoms, waist relaxed and stretched, hip circumference, and inseam length require particular attention because stretch fabrics behave differently when graded — a nominal increment may produce a different functional fit depending on the fabric's recovery properties.

See Runtang's custom t-shirt production capabilities and gym leggings OEM options for category-specific production context.

How to Document and Return Fit Feedback

When reviewing size set samples, measure against your spec sheet and record the actual measurement alongside the specified measurement for each POM. Any deviation outside your stated tolerance should be flagged in writing, with the actual measurement, the specified measurement, and the tolerance range noted for each affected point.

Verbal feedback on fit — "the chest feels tight" or "the length seems short" — is not actionable for a factory. A numbered measurement chart with deviations marked is. The clearer your written feedback, the fewer rounds of correction are needed before bulk approval.

Common Size Grading Mistakes That Cause Bulk Production Issues

Most fit-related bulk production problems trace back to a small set of repeatable errors in how brands submit their size grading information. Understanding these patterns helps brands catch the problem upstream, before a bulk run is cut.

Inconsistent grade increments across measurement points

If chest increases by 1 inch per size but side seam length stays fixed across all sizes, the garment proportions shift as the size goes up. For brands ordering woven tops or structured outerwear, this kind of inconsistency tends to produce correct fit in the base size and increasingly poor fit in the extremes. Each POM should have a defined increment, and those increments should reflect how the garment is meant to fit across the full range — not just how a single measurement scales.

No grading adjustment for stretch fabrics

Stretch fabric grades differently from woven fabric. A brand ordering seamless leggings or compression activewear that applies woven-fabric grade rules will typically see progressively worse fit as sizes increase. For stretch categories, the grade increment on key POMs like waist and hip should account for the fabric's stretch percentage and intended compression level. This is best confirmed during the size set sample stage, not assumed from the spec alone. The specific adjustments depend on fabric construction and are best discussed with the production team during the sampling stage.

Approving bulk from a single size sample

Approving a bulk order based on one size sample — even a well-fitting one — does not confirm grading accuracy. The sample confirms fit at the base size. It does not confirm that the factory has correctly applied grade rules across the other sizes. Requesting a size set for review before bulk approval is the standard checkpoint that catches grading errors while corrections are still practical.

Submitting a body measurement chart instead of a garment spec

A body measurement chart shows what body dimensions correspond to each size label. A garment spec shows the actual finished measurements of the garment. Factories work from garment specs — they cannot reverse-engineer your intended ease, fit preference, or silhouette from body measurements alone. Submitting body measurements in place of a garment spec is one of the most consistent causes of first-sample errors in new OEM relationships.

Mistake	What Happens	How to Avoid
Inconsistent grade increments	Fit degrades in larger/smaller sizes	Define a grade increment for every POM
No stretch adjustment	Compression/fit varies unpredictably by size	Discuss stretch-specific grading with factory during sampling
Approving from one size sample	Bulk has correct base size fit, other sizes untested	Always request a size set before bulk approval
Body chart vs garment spec	Factory cannot determine intended garment dimensions	Submit finished garment measurements, not body reference

Each of the four mistakes above is correctable at the pre-production stage. The same errors found after bulk cutting are not.

FAQ

What is a POM in clothing manufacturing?

POM stands for point of measure — a specific location on a garment where a measurement is taken. Common examples include chest width (measured a set distance below the armhole), body length (from the high point shoulder to the hem), and sleeve length (from the shoulder seam to the cuff). Each POM in a spec sheet should include the exact position and measurement method so the factory measures consistently across all production units.

Do I need to provide grade rules if I'm ordering from a Chinese OEM factory?

Yes. A Chinese OEM factory can follow your grade rules when they are clearly provided in the tech pack. If they are missing, the factory may ask for clarification or apply an internal reference rule. Providing your own grade rules as part of your tech pack submission is the most reliable way to ensure your size run fits the way you intend.

How many sizes should I include in my first OEM order?

For a first order, many early-stage brands choose a focused three- to five-size range to control SKU complexity before the fit is fully validated. The more practical question is whether to request a size set sample for all sizes before bulk approval. For a three-size run, reviewing all three at the pre-production stage is straightforward. For a wider range, reviewing at minimum the base size, the smallest, and the largest will surface any grading issues that affect the extremes.

Not sure whether your size spec is factory-ready? Share your tech pack or a rough measurement chart — we'll review what's there and let you know what needs to be confirmed before sampling.