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ream

A quantity of paper, 20 quires. Abbreviation, rm. Well into the 20th century a ream of writing paper contained 480 sheets and a ream of printing paper was 500 sheets, while suppliers of printers and publishers used a ream of 516 sheets. Today the standard ream of all types of paper is 500 sheets.

One sometimes sees it stated that 1 printer’s ream = 21½ quires.¹ If so, these are ordinary 24-sheet quires, not printer’s quires of 25 sheets.

1. for example, Alfred J. Martin.
Up-to-date Tables of Imperial, Metric, Indian and Colonial Weights and Measures…
London: T. Fisher Unwin, 1904.
Page 191.