Fire Emblem Heroes IV Calculator
Use this tool to estimate a unit’s Asset (boon) and Flaw (bane) by comparing neutral level 40 stats with observed stats.
Tip: enter manual corrections for merges, dragonflowers, support, blessings, bonus unit effects, skills, and any other stat boosts. The calculator subtracts those first, then evaluates IV differences.
| Stat | Neutral Lv40 | Observed Lv40 | Manual Correction | Delta After Correction |
|---|---|---|---|---|
| HP | — | |||
| ATK | — | |||
| SPD | — | |||
| DEF | — | |||
| RES | — |
How this FEH IV calculator works
In Fire Emblem Heroes, each hero has internal individual values (IVs) that shift stats up or down. Historically this is called an Asset and a Flaw, and many players still refer to them as boon/bane. This calculator compares a hero’s neutral level 40 stats against the numbers you actually see in-game.
Because heroes can gain stats from merges, dragonflowers, support, and other systems, this page includes a manual correction column. Put your non-IV boosts there. The calculator subtracts those values and then estimates what part of the difference is likely from IVs.
Step-by-step usage
1) Enter neutral stats
Use a trusted FEH database for your unit’s 5★ level 40 neutral values. Enter HP, Atk, Spd, Def, and Res.
2) Enter observed stats
Input the current stats your unit has in-game (same rarity/level context as your neutral reference).
3) Add manual corrections
- Merges
- Dragonflowers
- Ally/Summoner support effects
- Blessings and seasonal bonuses
- Visible skill boosts that are part of your comparison
If your hero is Resplendent, you can simply tick the checkbox to auto-subtract +2 from each stat.
4) Click Calculate
You’ll get per-stat deltas and a likely IV interpretation. A strong positive delta usually indicates Asset, while a strong negative delta usually indicates Flaw.
Interpreting the output
The result section gives you:
- Adjusted stat differences after removing entered corrections.
- Likely Asset candidates (stats with meaningful positive change).
- Likely Flaw candidates (stats with meaningful negative change).
- A simple conclusion line for easy reading.
If your output looks ambiguous, that usually means one of two things: either extra bonuses were not fully removed, or your unit configuration (such as merges/ascended traits) makes multiple interpretations possible.
Common FEH IV scenarios
Neutral or effectively neutral units
If all corrected deltas are near zero, your hero is probably neutral, merged in a way that hides original flaw impact, or otherwise stat-balanced by additional systems.
One clear positive and one clear negative
This is the classic pre-merge IV pattern: one boosted stat and one reduced stat. Example output might look like +Atk / -Spd.
Multiple positives, no negatives
This often appears on invested units where flaw penalties have been neutralized, or where ascended traits and extra bonuses complicate direct reading.
Why IV checking still matters in 2026
Even with modern skill power creep, small stat edges still decide doubles, damage thresholds, and survival checks. Good IV choices improve consistency in Arena, Aether Raids, and high-end PvE challenge maps. If you optimize only one thing on a hero, making sure your IV direction matches your build goal is usually a strong first move.
Quick best practices
- Always compare stats at the same rarity and level.
- Remove every known external bonus before drawing conclusions.
- Use this as an estimator when heavy investment is involved.
- For absolute precision, cross-check with a full hero simulator.
Disclaimer: FEH stat systems can be complex. This calculator is a practical estimator for player workflow and build planning.