What is the chance of Mehrune's Razor to proc?

Testing can be awfully bloody sometimes. Just ask Constance Michel:

For Science!

So I went around in god mode with the Mehrune's Razor and tested it on a bunch of NPCs after doing the following:

  1. Disable their AI via tai
  2. Set their health to 5000 via setav health 5000 (so they don't die to regular damage)
  3. Go on a rampage spree in Riften

Here are the # of hits before dying:

  • 15
  • 14
  • 1 (Super unlucky guard)
  • 114 (Super lucky guard)
  • 39
  • 3
  • 36
  • 51
  • 21
  • 46
  • 67
  • 28
  • 66
  • 66
  • 19
  • 70
  • 22
  • 76
  • 34
  • 18
  • 29
  • 36
  • 61
  • 47
    Average: 38.8333333 hits (stdev 26.8, which is quite high...)

This works out to be ~2.57% +/-1.78% margin of error

If anyone wants to provide more sample points, go right ahead. For now, I'm going to conclude that the chance to proc is roughly 2.5%


yx. might need to check his math. I get a mean of 40.7917 for the values he quoted, with a standard deviation of 26.8.

This means 955 hits were non-instant while 24 were instant-kill hits.

Combining this with my own data of roughly 849 hits with 31 instant-kills (plus a few more) gives a total of 1955 regular hits & 58 instant-kill hits.

I applied a Bayesian approach and set the prior density to a half-triangle that peaks at zero, since most people assumed it was small. The final result is:

(2.91 +- 0.74)%,

where the +- indicates a 95% probability interval. As a hunch, since game programmers might prefer round numbers, our data together suggests that 3% might be the true proc rate.


According to the UESP Mehrunes' Razor article, the chance of the Mehrunes' Razor instant kill effect activating is 2/101 or ~ 1.98%.

Note: This is the actual chance of activating, as this information was extracted from the game's files using the Creation Kit.