The ’21-foot rule’ is a concept theorizing that an adversary with a knife can potentially rush you from up to 21 feet away then attack before you can unholster your gun then fire two shots.


The ’21-foot rule’ is a guideline, not a strict rule. It’s the principle that assumes the average adversary can sprint for 21 feet in about 1.5 second with deadly intent carrying a knife or other melee weapon.

The second part of the “rule” is assuming the average police officer can unholster then fire off two shots within the same time frame of about 1.5 seconds.

This is an oversimplification of attempting to put a singular strategy on such a dynamic scenario of firearms close quarters combat, but as a guideline it can be quite useful.

At the least it serves as a self-defense training exercise direction to prepare against short-ranged edged / impact weapon attacks when armed only with a holstered or concealed handgun.

At best it gives you a higher defensive mindset by developing better tactical awareness and spatial reasoning that help you understand how to respond with your sidearm in such close quarters.


The ’21-foot rule” was originally conceived by Sergeant Dennis Tueller. He analyzed the distance an adversary with a knife would have to be for a police officer to be able to respond to a sudden lethal strike by drawing and firing their pistol from a holstered position.

Again, not as a policy or rule but as a flexible guideline, this concept can help you to take better CQC action as suppose to relying on reaction.

Instead of reacting to a gun / knife scenario, you can take decisive action because of a clearer sense of the reactionary gap and more efficient threat assessing.

Combatives action is always faster than combatives reaction and is almost always the better decision of the two. Having this “rule” in mind during such conflicts gives you that extra time and additional thought process to make the most optimal tactical choice.

However, the number / distance of 21 should be considered somewhat arbitrary as it can be less or more depending on the adversary’s physical capability, location terrain, weather / visibility and your own firearms proficiency and reflexes.

It is important to distinguish that this a suggestive guideline, not a standardized protocol. It’s not impossible to shoot the approaching assailant at 20 feet and you’re not necessarily out of danger at 22 feet.

The ’21-foot rule’ effectively demonstrates that an assailant can cover at least 21 feet before most people with firearms training can draw their weapon.

[OPTICS : ’21-Foot Rule’ Gun and Knife Example]