In tabletop roleplaying, attack bonus is the numeric outcome of your chance to hit a target with a weapon or spell attack. To determine attack bonus, you combine your relevant ability modifier, proficiency bonus when proficient, any applicable bonuses or penalties, and special circumstances such as advantage or cover. This guide explains the components, standard formulas, and frequent edge cases using verified rules and practical examples, so you can calculate results quickly at the table and build characters with reliable accuracy.
Core Components of Attack Bonus
An attack roll in D&D 5e uses a d20 plus modifiers. The attack bonus is the sum of those modifiers before rolling. Common contributors include your ability modifier for the attack, proficiency bonus if you are proficient with the weapon or spell, and any situational or class features that apply. Penalties such as disadvantage or impairment subtract from the total. Because different weapons and spells specify different ability scores and proficiency rules, the exact formula varies by character and situation. The next sections break these components into manageable parts.
How to Determine Attack Bonus for Melee and Ranged Weapons
For weapon attacks, the ability score used depends on the weapon and your fighting style options. For example, attacks with a longsword use Strength, while attacks with a ranged weapon such as a longbow typically use Dexterity. To determine attack bonus for a weapon attack, add your relevant ability modifier, your proficiency bonus if you are proficient with the weapon, and any other bonuses from class features or magic items. Table 1 lists common weapon types and the usual ability scores that govern their attack rolls.
Table 1: Weapon Types and Governing Ability
| Weapon Type | Governing Ability | Typical Use Case |
|---|---|---|
| Simple Melee | Strength | Club, dagger |
| martial Melee | Strength | Greatsword, greataxe |
| Simple Ranged | Dexterity | Light crossbow |
| martial Ranged | Dexterity | Longbow, hand crossbow |
| Spell Attacks | Spellcasting Ability | Spell save DC or spell attack roll |
Incorporating Proficiency and Fighting Style
Proficiency grants a bonus that improves as you gain levels. If you are proficient with the weapon or spell, add your proficiency bonus to the attack bonus. Fighters and other martial classes often gain Fighting Style features that provide a fixed bonus on attack rolls under certain conditions. For example, some styles grant a bonus when attacking with specific weapon groups. Table 2 shows typical proficiency bonus values by level range and includes examples of style bonuses to illustrate how they affect the total attack bonus.
Table 2: Proficiency Bonus and Example Fighting Style Impact
| Character Level | Proficiency Bonus | Example Fighting Style Bonus | Combined Modifier Example |
|---|---|---|---|
| 1–4 | +2 | +1 (e.g., Archery) | +3 total from these sources |
| 5–8 | +3 | +1 | +4 total |
| 9–12 | +4 | +1 | +5 total |
| 13–16 | +4 | +1 or +2 | +5 or +6 total |
| 17–20 | +4 | +2 | +6 total |
Magic Bonuses, Cover, and Special Conditions
Magic weapons and class features can grant bonuses to attack rolls that stack with other bonuses of the same type unless otherwise specified. Some conditions, such as half cover or three-quarters cover, impose penalties to attack rolls rather than adding bonuses. To determine attack bonus in these cases, add all positive modifiers first, then subtract penalties. Advantage grants two d20 rolls and you take the higher, which increases the expected value of the attack but does not change the written bonus on your sheet. Disadvantage uses the lower roll and reduces the expected result. Note that situational modifiers should be applied only when the rules specify their effect.
Spell Attacks and Concentration Checks
Spell attack rolls follow the same structure as weapon attacks, using your spellcasting ability modifier, proficiency if the spell requires it, and other applicable bonuses. To determine attack bonus for a spell attack, identify the spell’s attack type, the relevant ability, and whether you add proficiency. Concentration checks use a different formula, typically a DC, rather than a bonus to hit, but concentration itself can be broken by incoming damage, which is separate from the attack bonus used to hit with the original spell.
Step-by-Step Calculation Example
Worked example: a 5th-level fighter using a longsword with Strength 16, proficiency, and the Fighting Style archetype that grants +1 when using martial weapons. Ability modifier for Strength 16 is +3. Proficiency bonus at level 5 is +3. Fighting style adds +1. Attack bonus = +3 (Strength) +3 (proficiency) +1 (style) = +7. If using a magic weapon that adds +1, the total becomes +8. This illustrates how each component contributes and how to determine attack bonus consistently at the table.
Common Edge Cases and Clarifications
Some features, such as Bless, adddice rather than a flat bonus, so the attack bonus shown on your sheet may shift during the roll. Two-weapon fighting adds a small bonus to the secondary attack, as noted in the rules. If a feature allows you to add your proficiency bonus to certain attacks even when normally you do not, include it only where specified. Always confirm which ability score a weapon or spell specifies, and verify whether the proficiency bonus applies before adding modifiers.
Improving Accuracy Without Inflating Bonuses
Focus on ability improvements, timely ASIs, and selecting fighting styles and magic items that match your weapon choice. Prioritize features that increase your proficiency bonus or grant consistent flat bonuses over situational ones. Tracking your modifiers in a single reference sheet reduces errors and speeds up play. Understanding how to determine attack bonus helps you compare options and choose the combinations that maximize reliable hits over time.
Summary Checklist for Quick Reference
- Identify the weapon or spell and its governing ability score.
- Add your relevant ability modifier.
- Add your proficiency bonus if proficient with the weapon or spell.
- Include class features, fighting styles, and magic item bonuses as applicable.
- Apply penalties for cover, impairments, or other circumstances as written.
- Use advantage/disadvantage to roll two d20s and choose the appropriate result.
Frequently Asked Questions
Players often ask whether bonuses from different sources always stack, how to handle unfamiliar weapons, and how to adjust when rules change in a campaign. When in doubt, verify the specific wording of each feature and compare it to the standard formula above. This approach minimizes confusion and keeps your attack bonus consistent across sessions. Revisiting these fundamentals helps both new and experienced players maintain accuracy at the table.