Winning on the tabletop is not just about having a beautifully painted army or rolling sixes at the right time. It is about understanding the underlying probability of the game. This Warhammer 40k damage calculator helps you solve the complex math of combat in seconds, allowing you to focus on strategy rather than arithmetic.By using this tool, you can see exactly how effective a unit will be against any target in the game. You can stop guessing and start building your army lists based on hard statistical data. You can also visit our main calculator hub to find more tools designed to simplify your decision-making.

How to Use the Warhammer 40k Damage Calculator

Using the calculator is simple, but getting the most accurate results depends on entering the correct data from your index cards or codex. Follow these steps to get a precise damage estimate.

1. Enter Attacks and Accuracy: Start by entering the number of attacks your unit or weapon has. Then, input the Ballistic Skill (for shooting) or Weapon Skill (for melee).
2. Compare Strength and Toughness: Input your weapon’s Strength and your opponent’s Toughness. The calculator will automatically determine the required “To Wound” roll.
3. Input AP and Saves: Enter the Armor Penetration (AP) value of your weapon and the enemy’s Save characteristic. If the enemy has an Invulnerable Save, make sure to use the better of the two options.
4. Select Special Keywords: If your weapon has rules like Lethal Hits, Sustained Hits, or Devastating Wounds, toggle these options. This is crucial because these rules bypass standard math and drastically change the final result.
5. Review the Expected Damage: The calculator will provide the “Expected Value,” which is the average damage you can expect to deal. Use this number to decide if you need to commit more units to that specific target.

What is Mathhammer and Why Does It Matter?

If you want to win tournaments or just stop losing to your friends, you need to understand “Mathhammer.” This is the community term for the statistical engine that runs every phase of the game.

Most players make the mistake of looking at a weapon’s maximum damage. A veteran player looks at the “Expected Value” (EV). This is the average result you can expect over many games. High-level analysis, such as that found on Goonhammer, shows that understanding these averages is the difference between a casual player and a tournament winner. Our calculator takes the guesswork out of these averages so you can build a more reliable list.

How the 10th Edition Damage Sequence Works

The game follows a strict chain of events. Our calculator automates this entire process based on the variables you provide.

Variable	Definition	Role in Your Strategy
BS / WS	Ballistic or Weapon Skill	Your base accuracy for shooting or melee.
S vs T	Strength vs Toughness	Determines if your hits actually cause a wound.
AP	Armor Penetration	Reduces the effectiveness of the enemy’s armor.
Sv	Save Characteristic	The target’s defense, including Invulnerable Saves.
D	Damage	The amount of health lost per failed save.

The “Mathhammer” Formula Explained

To rank high in tournaments or just beat your friends, you need to understand the sequence of probability. We call this “Mathhammer.” It is the statistical engine behind every dice roll.

Our tool automates this specific chain of events:

The Semantic Variables:

• Ballistic/Weapon Skill (BS/WS): The raw chance to land a hit.
• Strength vs. Toughness: The comparison that dictates your “To Wound” roll.
• Save Characteristic (Sv): The enemy’s armor or invulnerable save.
• Armor Penetration (AP): The modifier that reduces the enemy’s save.

Practical Example: Lascannon vs. Battle Tank

Let’s apply this to a common scenario. You are firing a Lascannon (high strength) at a Leman Russ Battle Tank (high toughness).

The Statline:

• Attacks: 1
• Hit: 3+ (BS)
• Strength: 12 vs Toughness: 11 (3+ to wound)
• AP: -3 vs Save: 2+ (Modified to 5+)
• Damage: D6+1 (Average 4.5)

The Math:

1. Hit: 0.66 probability.
2. Wound: 0.66 probability.
3. Failed Save: The tank saves on 5+. It fails on 1, 2, 3, or 4. This is a 0.66 chance to bypass armor.

The Verdict:

You have roughly a 28% chance of pushing damage through with a single shot. This tells you that relying on one gun to finish off that tank is a risky gamble.

Manual Calculation: Running the Numbers Mid-Game

There are moments during a game where you cannot pull out a calculator. Knowing how to run a quick probability check in your head is a major tactical advantage.

1. Converting Dice Rolls to Decimals

To calculate the “Expected Value,” you first need to know your success rate for a single D6 roll:

• 2+: 0.83 (Very reliable)
• 3+: 0.66 (Standard)
• 4+: 0.50 (Coin flip)
• 5+: 0.33 (Risky)
• 6+: 0.16 (Desperation)

2. The Strength vs. Toughness Grid

In 10th Edition, the math for wounding has specific “breakpoints.” You can find the full official rules for these interactions on the Warhammer Community website.

• Strength is 2x Toughness: 2+ to wound.
• Strength is higher than Toughness: 3+ to wound.
• Strength equals Toughness: 4+ to wound.
• Strength is lower than Toughness: 5+ to wound.
• Strength is half (or less) than Toughness: 6+ to wound.

How Buffs and Stratagems Shift the Math

In modern 40k, basic stats are only half the story. The real damage comes from stacking modifiers.

Rerolls and Accuracy

A simple “Reroll 1s” aura might not seem like much, but it increases your total hits by roughly 16 percent. Full rerolls are even more powerful. If you have a 4+ Ballistic Skill with full rerolls, your accuracy jumps from 50 percent to 75 percent. Always look for ways to grant your high-damage units these rerolls through Leader abilities or Stratagems.

Plus One to Wound

The “+1 to Wound” modifier is widely considered the strongest buff in the game. It allows low-strength weapons to threaten heavy tanks. When you move from a 5+ to a 4+ to wound, you are increasing your wounding efficiency by 50 percent. Using the calculator to identify where these buffs are most effective can turn a mediocre unit into a tank-killer.

Dealing with Blast Weapons and Unit Size

If you are using a weapon with the Blast keyword, the math changes based on how many models are in the target unit. For every five models in the enemy unit, you add one extra attack to your weapon’s total.

• Against 1–4 models: No bonus.
• Against 5–9 models: +1 attack.
• Against 10–14 models: +2 attacks.

When calculating damage against large hordes like Orks or Tyranids, always remember to add these attacks into the calculator. This often makes Blast weapons significantly more points-efficient than high-strength, single-shot weapons when clearing objectives.

Understanding 10th Edition Special Rules (Keywords)

The damage sequence is often interrupted by special weapon keywords. These are essential to input correctly for an accurate calculation.

Anti-X and Devastating Wounds

The Anti-Keyword (like Anti-Vehicle 4+) means you always wound that specific target on a 4+ regardless of your Strength. When paired with Devastating Wounds, these critical wounds bypass armor saves entirely. This combination is currently one of the most lethal ways to deal with heavy units in the competitive meta.

Sustained Hits vs. Lethal Hits

Sustained Hits give you extra hits on a roll of a 6, which is great for weapons that already have high Strength. Lethal Hits allow a 6 to hit to automatically wound, which is better for low-strength weapons firing at high-toughness targets. Choosing the right buff based on your target is a key skill in Warhammer 40k.

Advanced Strategies: Target Priority and the Overkill Trap

One of the biggest mistakes players make is committing too much fire to a single target. If a unit has only two wounds left, firing 10 Lascannons at it is a waste of resources.

Use the damage calculator to figure out the minimum amount of fire needed to destroy a target with 80 percent certainty. This allows you to split your fire and take out multiple enemy units in a single turn. Reliability is usually better than “peak” damage in a tournament setting.

A Brief History of Warhammer Stats

The game has changed significantly since its release in 1987 as Rogue Trader. Back then, it was more of a roleplaying game than a competitive wargame. You often needed a Game Master to interpret rules and lookup tables.

Today, Games Workshop has streamlined the math into the Strength vs. Toughness comparison we use now. This shift has made the game faster and more accessible for tournament play, allowing tools like our damage calculator to provide instant, actionable data.

Frequently Asked Questions (FAQ)

How do I handle “Reroll 1s” in the calculator?

Rerolls drastically increase your consistency. Mathematically, rerolling 1s adds about 16% to your success rate for that specific step. If you have full rerolls to hit, your accuracy jumps significantly.

Does this tool work for 10th Edition?

Yes. The core math of Warhammer 40k (Hit > Wound > Save) remains consistent across 10th Edition. The calculator handles the probabilities regardless of the specific edition rules as long as you input the correct stats.

What is the average of a D3 or D6?

In Mathhammer, a D3 averages to 2. A D6 averages to 3.5. When calculating potential damage output over a long game, always use these averages rather than hoping for a maximum roll.

Master More Measurements

If you found this guide helpful for your tabletop strategy, check out our other precision tools:

• WCRA Calculator – Get accurate estimates for workers compensation liability.
• Main Calculator Hub – Find our complete collection of helpful tools.