40k Damage Calculator

What is a 40k Damage Calculator?

A 40k damage calculator is an indispensable tool for players of Warhammer 40,000, a popular tabletop wargame. It allows players to predict the statistical outcome of combat encounters between different units. By inputting the attacker's weapon characteristics (Attacks, Ballistic Skill/Weapon Skill, Strength, Armor Penetration, Damage) and the defender's defensive stats (Toughness, Save, Invulnerable Save, Feel No Pain, Wounds), the calculator provides an estimated number of wounds inflicted and the probability of achieving specific outcomes, such as destroying an enemy model.

This tool is crucial for list building, tactical planning, and understanding unit effectiveness. It helps players identify which units are best suited to engage specific threats, optimize their army compositions, and make informed decisions during gameplay.

Who Should Use This 40k Damage Calculator?

• Competitive Players: To min-max army lists and understand damage breakpoints.
• Casual Players: To learn game mechanics and explore unit interactions without needing complex math.
• New Players: To grasp the fundamentals of the combat phase and the impact of different statistics.
• List Builders: To validate unit choices against common enemy profiles.

Common Misunderstandings

It's important to remember that a 40k damage calculator provides averages and probabilities, not guarantees. Warhammer 40,000 is a dice-based game, and actual outcomes can vary due to random chance. Common misunderstandings include:

• Exact Outcomes: Expecting the exact calculated wounds every time. The calculator shows what's likely over many repeated engagements.
• "X+" Notation: Confusing "3+" with rolling a 3. "3+" means you need to roll a 3 or higher on a D6.
• Unitless Values: All values in this calculator (Attacks, Strength, Save, etc.) are specific game statistics, not real-world units like meters or kilograms.
• Ignoring Special Rules: Forgetting to account for specific unit abilities or stratagems that can significantly alter combat outcomes. This calculator includes common special rules like re-rolls, Sustained Hits, Lethal Hits, and Devastating Wounds.

40k Damage Formula and Explanation

The core of any 40k damage calculator lies in its underlying mathematical formulas, which simulate the dice rolls and modifiers of the game's combat phase. The calculation proceeds in several distinct steps: Hitting, Wounding, Saving, and applying Feel No Pain (FNP).

The simplified formula for Expected Total Wounds (including Mortal Wounds) is:

Expected Total Wounds = (Expected Hits * P(Wound) * P(Fail Save) * P(Fail FNP) * Damage) + Expected Mortal Wounds

Let's break down each component:

1. Expected Hits: This is the number of attacks multiplied by the probability of hitting, factoring in Ballistic Skill/Weapon Skill and any hit re-rolls or Sustained Hits.
2. Probability to Wound (P(Wound)): This depends on the attacker's Strength (S) versus the defender's Toughness (T).
   • S ≥ 2x T: Wounds on 2+
   • S > T: Wounds on 3+
   • S = T: Wounds on 4+
   • S < T: Wounds on 5+
   • S ≤ 0.5x T: Wounds on 6+
   This step also incorporates wound re-rolls and Lethal Hits (where critical hits automatically wound).
3. Probability to Fail Save (P(Fail Save)): This considers the defender's normal Save (Sv) and Invulnerable Save (Invuln), modified by the attacker's Armor Penetration (AP). The defender uses the better of their modified normal save or their Invulnerable Save. A natural 1 always fails a save.
4. Expected Damage Before FNP: This is the number of unsaved wounds multiplied by the weapon's Damage (D) characteristic.
5. Expected Mortal Wounds: If Devastating Wounds is active, critical wounds bypass the saving throw and inflict Mortal Wounds equal to the weapon's Damage.
6. Probability to Fail Feel No Pain (P(Fail FNP)): After all other damage, the defender may have a FNP ability, which allows them to ignore a portion of the incoming wounds on a successful dice roll.

Key Variables and Their Meaning

Practical Examples Using the 40k Damage Calculator

Let's illustrate the utility of this 40k damage calculator with a couple of common scenarios in Warhammer 40,000.

Example 1: Basic Infantry vs. Basic Infantry

Imagine a unit of 10 Space Marines (Attacks 2, WS 3+, S 4, AP 0, D 1) firing boltguns at a unit of 10 Ork Boyz (T 5, Sv 4+, Invuln None, FNP None, Wounds 1, Models 10).

• Attacker:
  • Attacks: 20 (10 models * 2 attacks each)
  • BS/WS: 3+
  • Strength: 4
  • AP: 0
  • Damage: 1
  • Re-roll Hits: None
  • Re-roll Wounds: None
  • Sustained Hits: None
  • Lethal Hits: No
  • Devastating Wounds: No
• Defender:
  • Toughness: 5
  • Save: 4+
  • Invulnerable Save: None (7+)
  • Feel No Pain: None (7+)
  • Wounds per Model: 1
  • Models in Unit: 10

Expected Results:

Inputting these values into the 40k damage calculator would yield approximately:

• Expected Hits: 13.33
• Expected Wounds: 6.67
• Expected Mortal Wounds: 0.00
• Expected Damage (Before FNP): 4.44
• Expected Total Wounds: 4.44
• Probability to Destroy 1 Model: Approximately 98% (very high chance to kill at least one Ork Boy)

This indicates that a unit of 10 Space Marines is likely to eliminate 4-5 Ork Boyz in a single volley, significantly reducing the target unit's strength.

Example 2: Anti-Tank Weapon vs. Heavy Vehicle

Consider a Lascannon (Attacks 1, BS 3+, S 12, AP -3, D 6) targeting a Land Raider (T 12, Sv 2+, Invuln None, FNP None, Wounds 16, Models 1).

• Attacker:
  • Attacks: 1
  • BS/WS: 3+
  • Strength: 12
  • AP: -3
  • Damage: 6
  • Re-roll Hits: None
  • Re-roll Wounds: None
  • Sustained Hits: None
  • Lethal Hits: No
  • Devastating Wounds: No
• Defender:
  • Toughness: 12
  • Save: 2+
  • Invulnerable Save: None (7+)
  • Feel No Pain: None (7+)
  • Wounds per Model: 16
  • Models in Unit: 1

Expected Results:

The 40k damage calculator would show:

• Expected Hits: 0.67
• Expected Wounds: 0.44 (S12 vs T12 wounds on 4+)
• Expected Mortal Wounds: 0.00
• Expected Damage (Before FNP): 2.96 (Modified save for Land Raider becomes 5+ due to AP -3)
• Expected Total Wounds: 2.96
• Probability to Destroy 1 Model: Approximately 0% (a single Lascannon hit is highly unlikely to destroy a Land Raider outright)

This example highlights that even powerful weapons might need multiple shots or supporting fire to take down resilient targets. If we were to change the Lascannon to have `Devastating Wounds`, the expected mortal wounds would increase, bypassing the save entirely and making it more effective.

How to Use This 40k Damage Calculator

Using this 40k damage calculator is straightforward, designed to give you quick and accurate insights into combat probabilities. Follow these steps to get the most out of the tool:

1. Input Attacker Profile:
   • Attacks (A): Enter the total number of attacks your unit makes. If a unit has multiple models, multiply the attacks per model by the number of models.
   • BS/WS: Select the Ballistic Skill (for shooting) or Weapon Skill (for melee) of your unit. This is represented as "X+".
   • Strength (S): Input the Strength characteristic of the weapon being used.
   • Armor Penetration (AP): Enter the AP value as a negative number (e.g., -1 for AP -1).
   • Damage (D): Enter the numerical damage value of the weapon.
2. Select Attacker Special Rules:
   • Re-roll Hits/Wounds: Choose "None," "1s," "Failed," or "All" based on your unit's abilities or stratagems.
   • Sustained Hits: Select the number of additional hits generated on a critical hit (usually a 6+).
   • Lethal Hits: Check this box if your critical hits automatically cause critical wounds.
   • Devastating Wounds: Check this box if critical wounds cause mortal wounds equal to the weapon's Damage.
3. Input Defender Profile:
   • Toughness (T): Enter the Toughness characteristic of the target unit.
   • Save (Sv): Select the normal Save characteristic of the target unit.
   • Invulnerable Save (Invuln): Select the Invulnerable Save of the target unit, if any. Choose "None (7+)" if they don't have one.
   • Feel No Pain (FNP): Select the Feel No Pain characteristic of the target unit, if any. Choose "None (7+)" if they don't have one.
   • Wounds per Model: Enter the total wounds a single model in the target unit has.
   • Models in Unit: Input the current number of models in the target unit.
4. Interpret Results:
   • The calculator will automatically update with the Expected Total Wounds (highlighted), along with intermediate values like Expected Hits, Expected Wounds, Expected Mortal Wounds, and Expected Damage before FNP.
   • Probability to Destroy 1 Model indicates the chance of inflicting enough damage to remove at least one model from the target unit.
   • The chart visually represents the probability distribution of total wounds inflicted.
5. Copy Results: Use the "Copy Results" button to easily transfer the calculated outcomes to your notes or discussions.
6. Reset: Click the "Reset" button to revert all inputs to their default intelligent values, allowing for quick new calculations.

Remember that all values are game statistics and are unitless in the traditional sense. The calculator provides an average expectation; actual dice rolls may vary.

Key Factors That Affect 40k Damage

Understanding the interplay of various statistics is crucial for mastering the combat phase in Warhammer 40,000. This 40k damage calculator helps illuminate how each factor contributes to the final outcome. Here are the most significant factors:

• Volume of Attacks: More attacks generally mean more opportunities to hit and wound. Units with many low-strength, low-AP attacks can overwhelm targets with poor saves or low Toughness through sheer volume, even if individual hits are weak.
• Ballistic Skill (BS) / Weapon Skill (WS): This determines how accurately your unit hits. A 2+ BS/WS is significantly better than a 4+, as it doubles your chance to hit. Improving this (e.g., with re-rolls) has a profound impact.
• Strength (S) vs. Toughness (T): This is the primary determinant of wounding probability. Wounding on 2+ (Strength at least double Toughness) is incredibly efficient, while wounding on 6+ (Strength less than half Toughness) is highly inefficient. Matching Strength to Toughness is key to effective wounding.
• Armor Penetration (AP) vs. Save (Sv): AP reduces the target's armor save. A high AP weapon against a unit with a poor save can bypass their defenses entirely. Even a small amount of AP can dramatically increase damage against units with common 3+ or 4+ saves.
• Damage (D) Characteristic: This is the number of wounds each successful, unsaved hit inflicts. High damage weapons are crucial for taking down multi-wound models and vehicles. A weapon with D3 or D6 damage adds variability but increases the potential for spike damage.
• Invulnerable Saves (Invuln): These saves ignore AP entirely, making them invaluable against high-AP weaponry. Units with good invulnerable saves are very resilient against dedicated anti-tank weapons.
• Feel No Pain (FNP): This ability provides a final layer of defense, allowing a unit to ignore wounds after all other saves have been made. It effectively reduces the total damage taken, making units significantly more durable.
• Re-rolls (Hits & Wounds): Re-rolling failed hits or wounds dramatically increases the consistency and average output of a unit. Re-rolling '1s' is common, while 're-rolling failed' is extremely powerful.
• Critical Hit/Wound Abilities (Sustained Hits, Lethal Hits, Devastating Wounds): These special rules introduce powerful effects on specific dice rolls:
  • Sustained Hits: Generate extra hits on critical hits, boosting volume.
  • Lethal Hits: Critical hits automatically wound, bypassing the Strength vs Toughness comparison, great against high Toughness targets.
  • Devastating Wounds: Critical wounds become mortal wounds, bypassing saves (including invulnerable saves) and FNP for the initial damage.

Frequently Asked Questions (FAQ) about 40k Damage Calculation

Q: What does "X+" mean in Warhammer 40,000 statistics like BS/WS 3+ or Save 4+?

A: "X+" means you need to roll a result of X or higher on a six-sided dice (D6) to succeed. For example, a BS 3+ means you need to roll a 3, 4, 5, or 6 to hit. A Save 4+ means you need to roll a 4, 5, or 6 to pass your save.

Q: Why is the "Expected Total Wounds" result not a whole number?

A: The calculator provides an average or expected value based on probabilities. Since dice rolls are random, you won't always roll the exact average. The fractional number represents the statistical mean outcome over many repetitions of the same combat scenario.

Q: Does this 40k damage calculator account for all special rules in the game?

A: This calculator includes many common and impactful special rules like re-rolls, Sustained Hits, Lethal Hits, and Devastating Wounds. However, Warhammer 40,000 has a vast array of unique unit abilities, stratagems, and enhancements. It's impossible for a general calculator to include every single one. Always consider any additional rules specific to your units or mission.

Q: How accurate is this 40k damage calculator?

A: The calculator is mathematically accurate based on the probabilities of dice rolls and the rules incorporated. It provides the expected statistical outcome. The accuracy of your battle results depends on whether you've entered all relevant stats and special rules correctly.

Q: What's the difference between a normal Save (Sv) and an Invulnerable Save (Invuln)?

A: A normal Save (Sv) is modified by the attacker's Armor Penetration (AP) characteristic. An Invulnerable Save (Invuln) is never modified by AP. If a unit has both, it uses the better of its modified normal save or its Invulnerable Save. For example, if a unit has a 3+ save and a 4+ invulnerable save, and is shot by an AP -2 weapon, its normal save becomes a 5+. Since 4+ is better than 5+, it would use its 4+ invulnerable save.

Q: Can I use this calculator for other wargames?

A: This calculator is specifically designed for Warhammer 40,000 (10th Edition ruleset). While some wargames share similar mechanics, the specific interactions of Strength, Toughness, AP, Save, and special rules are unique to 40k. Using it for other games would likely produce inaccurate results.

Q: What are Mortal Wounds, and how do they differ from normal wounds?

A: Mortal Wounds are a special type of damage that bypass all saving throws (both normal and invulnerable saves) and are directly applied to the target's Wounds characteristic. They can only be mitigated by a Feel No Pain ability. Devastating Wounds is a common ability that converts critical wounds into Mortal Wounds.

Q: How do re-rolls work in the calculator?

A: When you select a re-roll option (e.g., "Re-roll 1s"), the calculator automatically adjusts the probability of success. If you re-roll 1s, any dice that rolled a 1 get a second chance to succeed. If you re-roll failed rolls, all unsuccessful rolls get a second chance, significantly increasing the chance of success.

Related Tools and Internal Resources

To further enhance your Warhammer 40,000 experience and dive deeper into the game's mechanics, explore these related tools and guides:

• Comprehensive 40k Army Builder: Plan and optimize your Warhammer 40,000 army lists for competitive play.
• Warhammer 40k Unit Review Guide: In-depth analysis of popular units and their battlefield roles.
• Beginner's Guide to Warhammer 40,000: Start your journey into the grim darkness of the far future.
• 40k Stratagem Deep Dive: Master the tactical advantages provided by various stratagems.
• Advanced 40k Mission Tactics: Learn how to play objectives and win games.
• Understanding 40k Terrain Rules: Optimize your movement and cover saves on the battlefield.