March 24, 2018

Great Weapon Master and Sharpshooter 5e Calculator

Dungeons and Dragons

The Great Weapon Master and Sharpshooter 5e feats are two of the most powerful feats in the game. They allow you to make an attack at a reduced chance to hit in order to deal a considerable amount of bonus damage. I’m currently playing an Arcane Archer Fighter that has the Sharpshooter feat. I wanted a way to figure out when I should be using my Sharpshooter feat in battle as opposed to a regular attack. That lead me to creating this spreadsheet.

The Feats

Both of these feats have perks other than the increased damage. This post and the spreadsheet, however, will focus on the damage dealing portion of both feats.

Great Weapon Master – PHB pg167

  • On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.
  • Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you can add +10 to the attack’s damage.

Sharpshooter – PHB pg170

  • Attack at long range doesn’t impose disadvantage on your ranged weapon attack rolls.
  • Your ranged weapon attacks ignore half cover and three-quarters cover.
  • Before you make an attack with a ranged weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack’s damage.

Use Case

The optimal way of using Great Weapon Master and Sharpshooter is to use them when the damage outweighs the increased chance of missing. As stated in the description of both feats, you have to declare that you are going to be using Great Weapon Master or Sharpshooter before you attack. This presents an element of risk. The +10 damage is very powerful, but a -5 penalty to hit does make you considerably less likely to hit than you normally would be. In order to confidently use either of these feats you have to first determine the target creature’s AC.


Here are two ways you can go about determining a creature’s AC that are fair to the game.

  1. Ask the DM for a description of the armor the creature is wearing, or if they have noticeably tough skin (natural armor). This provides a role-play opportunity as well!
  2. Take note of the attacks. If you notice that an attack roll of 14 hits the creature, but a 12 misses you know that the creature’s AC is either 13 or 14.

The Spreadsheet

I did some research online to determine how I should go about calculating my target AC. I found the formula here. Desamir, the author of the formula goes into detail how they went about creating the formula. It’s a great read if you want to learn more about the formula than the overview that I will be giving!

Great Weapon Master and Sharpshooter 5e

Calculation using my Arcane Archer’s stats


Attack Modifier: Your attack modifier which can be calculated by adding the appropriate stat (STR or DEX), your proficiency, and any additional bonuses such as the Archery Fighting style. Do not account for the -5 to attack in this cell, it is already in the formula.

Bonus Attack Modifiers: Any magical effects that increase or decrease your damage should be input here.

Damage Die: Select from the damage dice I have listed. I have converted these dice in the formula to use their average rolls so you cannot input your own.

Bonus Damage: Any magical effects that increase or decrease your damage should be input here. Do not account for the +10 damage in this cell, it is already in the formula. Example: a +2 long bow gives +2 damage.

Estimated Enemy AC: The AC of your target. This is an optional cell.

Enemy AC Threshold: The value in this cell is the point where you can optimally Power Attack (-5/+10). If you are attacking an enemy below the Enemy AC Threshold it is worthwhile to Power Attack. This is calculated based on your Attack Modifiers and Damage information that you input into their appropriate cells.

Power Attack: A -5/+10 attack using either the Great Weapon Master or Sharpshooter 5e feats.

SHOULD YOU POWER ATTACK?: This outputs either a yes or a no. If the Estimated Enemy AC is lower than the Enemy AC Threshold, the box will be colored green and say “YES”. Otherwise, the box will be colored red and say “NO”. This is an optional cell.

The Formula

Great Weapon Master & Sharpshooter 5e

Credit: Desamir & Giant in the Playground Forum

The attack bonus is your character’s attack modifier not including the -5 penalty to hit from either Great Weapon Master or Sharpshooter. This is subtracted by the average damage your weapon deals (not including the +10) divided by 2. Finally we add 16 which is the calculated constant. 

This formula determines what the Maximum AC is that you should attack with a Power Attack rather than a regular weapon attack. As long as the AC of your target is lower than the Maximum AC you calculated, you should Power Attack. For example if the output is 18.5 if the target’s AC is 18 or lower you should Power Attack.

Here’s an example calculation using my Arcane Archer’s bonuses:

  • +4 Dexterity Modifier
  • +3 Proficiency
  • +2 from the Archery Fighting Style
  • Longbow that deals 1d8 damage (4.5 average)

Maximum AC = 4 + 3 + 2  – (4.5 / 2) + 16
Maximum AC = 9 – 2.25 + 16
Maximum AC = 22.75

Based on this calculation I should be Power Attacking any creature with 22 or lower AC.


My friends and I did some extensive testing to ensure that the spreadsheet made sense and was accurate. Through this we came upon some interesting findings. Between Great Weapon Master and Sharpshooter, Sharpshooter had a noticeably higher AC Threshold. This was due to two reasons.

The first reason was that ranged weapons on average deal less damage than heavy melee weapons. Ranged weapons deal between 1 and 1d10 damage. Heavy weapons deal between 1d10 and 2d6 damage. Because ranged weapons generally deal less damage, it is more attractive to try to fish for that +10 damage using Sharpshooter. Since heavy weapons deal more damage on average, the formula places more value on a hit with a heavy weapon.

The second reason is that Fighters and Rangers have access to the Archery Fighting Style. This grants them a +2 to hit when using a ranged weapon. In 5e RAW there is no such bonus strictly for heavy weapons.

Feel free to give me any suggestions or additional features you might have for the spread sheet. I may continue working on it as this is a fairly rough draft on my end.

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