Method of sale

Liquids and solids

On this page11

The wording Which gives a liquid two routes And only the weight route has a tare problem Dry goods have three The sentence after the list is the one that bites Which is a comparability requirement So price per unit, in the unit the category uses Trade custom is a real exception and a narrow one Mixed carts are where this goes wrong Put the method on the shelf edge References

A liquid has two lawful methods. Only one of them involves tare.

The wording

"Except as otherwise provided by the Director or by firmly established trade custom and practice, (a) commodities in liquid form shall be sold by liquid measure or by weight; and (b) commodities not in liquid form shall be sold by weight, by measure, or by count."

Which gives a liquid two routes

Liquid measure, meaning fluid ounces or litres, or weight. Dish soap, laundry liquid, shampoo and surface cleaner can be sold either way.

And only the weight route has a tare problem

Measuring a volume into a container says nothing about what the container weighs. For a small shop that is a real simplification and it is worth choosing deliberately rather than defaulting to the scale.

Dry goods have three

Weight, measure or count. Flour and rice are sold by weight in practice; measure and count exist for commodities where they make sense.

The sentence after the list is the one that bites

"The method of sale shall provide accurate and adequate quantity information that permits the buyer to make price and quantity comparisons."

Which is a comparability requirement

A price that a customer cannot compare to the supermarket is not adequate quantity information. Pricing refill soap per pump, or per jar, defeats exactly that.

So price per unit, in the unit the category uses

Per fluid ounce or per litre for a liquid, per pound or per kilogram for a dry good. The comparison the customer wants to make is against the bottle they used to buy.

Trade custom is a real exception and a narrow one

"Firmly established trade custom and practice" is in the text. It is not a licence to invent a unit; it is recognition that some commodities have a settled way of being sold.

Mixed carts are where this goes wrong

A customer refilling shampoo by volume and buying oats by weight is two methods at one counter. Both are lawful and the receipt has to make each one legible.

Put the method on the shelf edge

Price per fluid ounce beside the soap, price per pound beside the oats. It costs a label and it is the whole of the comparability requirement in practice.

References

NIST Handbook 130, 2023, Uniform Weights and Measures Law, Section 16, Method of Sale: "Except as otherwise provided by the Director or by firmly established trade custom and practice, (a) commodities in liquid form shall be sold by liquid measure or by weight; and (b) commodities not in liquid form shall be sold by weight, by measure, or by count. The method of sale shall provide accurate and adequate quantity information that permits the buyer to make price and quantity comparisons." Section 17, Sale from Bulk, applies its delivery-ticket requirement to "all bulk sales in which the buyer and seller are not both present to witness the measurement", to bulk heating fuel deliveries, and to other bulk sales specified by the director. nist.gov

Written from NIST Handbook 130, 2023 edition, and from the catalog as it stood on 19 October 2026. Handbook 130 is a compilation of model laws rather than federal law, and states adopt it in different forms, from different years, or not at all; the binding text is your state's. Nothing here concerns whether a scale is legal for trade, which is Handbook 44 and a state device approval, or the retail food rules for refilling a customer's food container, which belong to whoever licenses the shop.