what does "is off by" mean in this sentence?

If the height of a single step is off by as little as two millimeters...

  • 2
    off means inaccurate (as with a measurement) or not conforming to dimensional specifications (as with a manufactured object).
    – TimR
    Commented Mar 16, 2017 at 21:45

2 Answers 2


| be off by| means to be less or more than what a measurement should be. Any measurement: time, distance, height, width, weight, etc.

The wall measures 6 feet 2 inches, so the wallpaper has to measure the same thing. If the wallpaper is only 6 feet, it is off by 2 inches.

The man ran a mile in five minutes. [less] You're off by three. [in other words you ran it in eight]. [more]

Your ideal weight as a man should be 85 kilos for your height. But you only weigh 80 kilos. You are off by five. [less]

The time is 6 o'clock according to your watch. Mine is off by two hours. [Context will tell if it is supposed to 8 or 4 o'clock.] [travel and time zones]

  • What's the opposite of "off by" in this context? Commented Apr 17, 2019 at 10:53
  • 1
    @Kumarsadhu There is no opposite of "to be off by x" in this context. The idea of off relates to a measurement of some kind (time, distance, weight, etc.) and can be more than or less than some amount depending on the context. Only context will tell which it is.
    – Lambie
    Commented Apr 17, 2019 at 14:41
  • I got it, sir. Thank you. Commented Apr 17, 2019 at 14:45
  • 1
    @Kumarsadhu Thank you for your question. I'm a woman but there's no need to say Ma'am. :)
    – Lambie
    Commented Apr 17, 2019 at 14:48
  • 1
    @Kumarsadhu It depends on your "standard". It does not mean an increase/decrease per se. If your standard rate is 1,000 rupees per widget, then 1,250 or 750 would be off by 250, up or down. If the standard time for a machine cycle is 25 minutes, and it only runs 20 minutes or 30 minutes, it is off by 5 minutes. The amount something is off, up or down, is in relation to some standard measurement implied or given in a context.
    – Lambie
    Commented Apr 17, 2019 at 15:16

"is off by" means "is wrong or inconsistent by this amount". We normally expect stairs to all be the same size. If you are walking up a flight of stairs and one is a little different from the others, this can be very disconcerting. So they're saying that one step is a slightly different height than other steps.

We routinely talk about a measurement being "off by" some amount. Like, "When you set the flux on the hyperdrive, if you're off by more than 5% the engines may explode."

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