back-of-an-envelope

back-of-an-envelope (not comparable)

1. Alternative form of back-of-the-envelope
   • 1979 February 22, Thomas F[rancis] Eagleton, “Department of Labor: Labor-management Services Administration: Statement of Jack A. Warshaw, Deputy Assistant Secretary for Labor-management Relations [...]”, in Departments of Labor and Health, Education and Welfare and Related Agencies Appropriations for Fiscal Year 1980: Hearings before a Subcommittee of the Committee on Appropriations, United States Senate, Ninety-sixth Congress, First Session: Part 1 […], Washington, D.C.: U.S. Government Printing Office, →OCLC, page 464:

     On one defense item, somebody kept referring to it as a back-of-an-envelope cost estimate. Do you have a back-on-an-envelope cost estimate?

   • 1996, T[homas] W[illiam] Körner, “Biology in a Darkened Room”, in The Pleasures of Counting, Cambridge, Cambridgeshire: Cambridge University Press, published 2002, →ISBN, part II (Meditations on Measurement), pages 112–113:

     The reader will not need to be warned that the calculations involved are of the back of an envelope type and statements of the form ‘a equals b’ should be read ‘a equals b approximately’ or even ‘with a bit of luck, a and b will be of the same order of magnitude’.

   • 1998, Paul Lawrence Rose, “The Bomb as Reactor: The U235 Bomb Misconceived, 1940”, in Heisenberg and the Nazi Atomic Bomb Project: A Study in German Culture, Berkeley; Los Angeles, Calif.; London: University of California Press, →ISBN, page 115:

     Misapplying a basic feature of diffusion theory, [Werner] Heisenberg arrived at an impossibly high figure for a critical mass of pure U235. This was done by means of a seductively simple "back of an envelope" calculation in 1940, […]

   • [2021 March 24, Christian Wolmar, “Railways Must Sell Themselves and Offer a Better Product”, in The Railway Magazine, number 927, Sutton, London: IPC Transport Press, →ISSN, →OCLC, page 46:

     Now, those Treasury mandarins unfamiliar with the railway might assume on the back of an envelope that if only 80% of trains are running, then that will cost 20% less. If only it were that simple.]