Section 4.1.5 of the Apollo Program Summary Report states

The major design criteria for the Saturn I were:

a. Minimum vehicle lift-off weight to thrust ratio

I've usually seen the reverse ratio being used here (especially for engines): thrust-to-weight ratio or TWR.

Was the weight-to-thrust ratio used much in the past? Is it still used today? If not, approximately when did the terminology change?

  • $\begingroup$ In general it's preferable to use quantities that don't have an inherent negation - "bigger is better". "Speed", not "Slowness", "Heat", not "Cold", etc. TWR is related to acceleration. WTR would be just stalling point. $\endgroup$
    – SF.
    Jul 14, 2019 at 19:53

1 Answer 1


According to Google NGrams, "weight to thrust" was more popular for a brief period around 1950, but "thrust to weight" became completely dominant beginning in the 1960s:

enter image description here

"Weight to thrust" is still occasionally used, possibly more often in discussion of aircraft where the norm is that weight exceeds thrust. In a google search I also see many instances of "weight to thrust" being used where "thrust to weight" is clearly meant.

  • 1
    $\begingroup$ It's important (very important!) to take Google Ngrams with a huge grain of salt. (1) It looks at books and books only, and not in technical journals or conference papers. (2) It sometimes gets the dates very wrong. Just two days ago I was looking for a book on a programming language and found Google had publishing dates going back to the 1600s. (3) Very small results (e.g., 0.000008%, the top of the scale in the linked graph is very, very small) should be views as somewhat suspect. $\endgroup$ Jul 14, 2019 at 21:06

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