Build a size guide that explains measurements rather than guarantees

A size guide is useful only when the customer understands what was measured. “Medium” does not explain a garment's actual dimensions, and a single length does not tell someone whether a bag will hold the object they want to carry.

Create the guide from the product, not from a generic chart found elsewhere. Your aim is to support a sensible comparison without promising that a measurement guarantees fit for every person or use.

Define the measurement type

For clothing, distinguish a body measurement from a finished-garment measurement. They answer different questions. For a bag or pouch, distinguish outside dimensions from usable internal space where that difference matters.

Explain whether an item is measured flat, around its circumference, stretched or unstretched. Do not assume that a customer will infer the method from the number.

If you cannot establish the method reliably, measure again before publishing. A precise-looking chart with unclear definitions can be worse than no chart because it creates false confidence.

Measure representative products consistently

Choose the points you will measure and document them with a clear photograph or diagram you have the right to use. Use the same method across sizes.

Record units prominently. Mixing centimetres and inches without labels invites mistakes. If you provide both, check the conversion and rounding rather than independently guessing a second number.

For handmade products, identify any supported tolerance or normal variation from your actual production process. Do not invent a universal allowance or use “handmade” to excuse a substantially inaccurate chart.

Present only useful comparisons

A compact guide should help the buyer distinguish the options that actually exist. Avoid adding rows for sizes you do not sell simply because a template includes them.

For a laptop sleeve, compare the device's physical dimensions with the supported internal space. Screen diagonal alone does not describe the whole device.

Show how to compare at home

Suggest comparing the guide with an item the customer already uses comfortably, using the same measurement method where practical. Explain the comparison without making a personal-fit guarantee.

For example, a buyer considering a pouch can measure the objects they intend to carry and inspect the opening as well as the overall size. A narrow opening can matter even when the interior dimensions look sufficient.

For garments, avoid unsupported body-type promises. If a customer needs specialist fitting advice, acknowledge the limitation of a general product guide rather than pretending a chart can resolve every concern.

Connect the guide to the correct product

Place or link the relevant information where the customer chooses the size. A site-wide chart is inappropriate if different product families use different cuts or measurement methods.

Check that the selected variant's label appears exactly as the chart names it. “Large” in the selector and “L2” in the guide need an explanation if they refer to the same option.

If a supplier or pattern changes, review the guide before selling the new stock under the old measurements. Historical orders may need the earlier specification preserved in your records.

Check the photographs for contradictory scale

Styling can distort perceived size. A product held by a person, placed beside an object or photographed close up needs enough context to prevent an unintended impression.

Use a scale reference that is understandable to your audience and label it where necessary. Do not use an image of one size beside the dimensions of another without saying so.

The photography checklist covers the broader role of scale and detail images. The chart and photograph should support each other, not tell different stories.

Learn from size-related questions and returns

Record the information gap when customers repeatedly ask the same question. Do not automatically conclude that they failed to read the guide; the guide may be difficult to interpret or hard to find.

Where a complaint reveals an inaccurate measurement, correct the information and handle affected orders through your proper support process. Keep the correction traceable.

Use catalogue preparation to check the full listing. A useful size guide ends with a clearer decision, including the possibility that the product is not suitable. That is better than obtaining an order through a promise the item cannot meet.