Equipment Sizes

In most campaigns, you can use or wear any equipment that you find on your adventures, within the bounds of common sense. For example, a burly half-orc won't fit in a halfling's leather armor, and a gnome would be swallowed up in a cloud giant's elegant robe.

The DM can impose mare realism. For example, a suit of plate armor made for one human might not fit another one without significant alterations, and a guard's uniform might be visibly ill-fitting when an adventurer tries to wear it as a disguise.

Using this variant, when adventurers find armor, clothing, and similar items that are made to be worn, they might need to visit an armorsmith, tailor, leatherworker, or similar expert to make the item wearable. The cost for such work varies from 10 to 40 percent of the market price of the item. The DM can either roll 1d4 × 10 or determine the increase in cost based on the extent of the alterations required.

Source: PHB, page 145