Calculate your League of Legends Effective Hit Points (EHP) instantly. Determine exact armor damage reduction percentages to optimize your champion durability builds.
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Technical Specification: Free League of Legends EHP Calculator
1. Overview
A single-file, client-side utility designed to help players calculate Effective Hit Points (EHP) based on League of Legends defensive mechanics. The app provides instant feedback on how armor stats impact survivability.
2. Technical Constraints
- No Persistence: Strictly no
localStorage,sessionStorage, or cookies. The app must be 100% stateless. - Architecture: Single HTML file containing embedded CSS and Vanilla JavaScript.
- Frameworks: No external frameworks. Only standard browser APIs.
- Compatibility: Must function inside a sandboxed iframe. No
alert(),confirm(), orprompt(). - No Branding: Absolutely no mention of specific game titles in the UI branding; use purely descriptive labels.
3. UI Layout
- Header: Simple, clean, centered text: "Effective Hit Points Calculator".
- Input Section (Left/Top):
- Numeric Input: "Current Health (HP)"
- Numeric Input: "Total Armor"
- Real-time updates: Inputs must trigger a recalculation on every
inputevent.
- Results Section (Right/Bottom):
- Large Display: "Effective Hit Points (EHP): [Value]"
- Secondary Metric: "Physical Damage Reduction: [Percentage]%"
- Visualization: A simple CSS-based progress bar showing Base HP vs. EHP gained via Armor.
4. Color Palette
- Background:
#FFFFFF(Pure white) - Primary Accent:
#2563EB(Professional blue) - Text:
#1F2937(Dark slate gray) - Secondary Text:
#6B7280(Medium gray) - Borders/Cards:
#E5E7EB(Light gray) - Shadows: Soft, subtle drop shadows (
0 4px 6px -1px rgba(0, 0, 0, 0.1)) to create depth.
5. Animations & Interactions
- Smooth Transitions: All inputs and output values should use
transition: all 0.2s ease-in-outfor hover effects and numeric updates. - Responsive Design:
- Desktop: Two-column grid (Input vs. Output).
- Mobile: Single-column stack with generous padding and clear, large touch targets.
- Micro-interactions: Subtle scaling effect on input focus and a gentle "pop" animation when the EHP result updates.
6. Calculation Logic (Javascript)
EHP = CurrentHP * (1 + (Armor / 100))DamageReduction = (Armor / (100 + Armor)) * 100- Results must be clamped to two decimal places for readability.
- Validation: If negative numbers or non-numeric characters are entered, default to 0 to prevent UI breakage.
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Frequently Asked Questions
Everything you need to know about using this application.
How is Effective Hit Points (EHP) calculated in League of Legends?
Effective Hit Points (EHP) is calculated by multiplying your total Health by the damage multiplier provided by your armor. The formula is: EHP = Health * (1 + (Armor / 100)). This metric represents the total raw physical damage your champion can sustain before reaching zero health. By focusing on EHP rather than raw health, players can make informed decisions about whether to build more Health or Armor. Our tool provides this calculation in real-time, helping you optimize your defensive itemization to withstand physical damage bursts in competitive scenarios.
Why does armor damage reduction have diminishing returns?
In League of Legends, Armor provides damage reduction based on the formula: Damage Reduction = Armor / (100 + Armor). While each point of armor technically adds 1% EHP increase, the percentage of damage mitigated follows a curve that approaches 100% but never reaches it. This means that the more armor you have, the less additional damage reduction you gain from each new point. Understanding this allows players to recognize when they have reached a point of diminishing utility, where investing in health items might actually provide a greater survivability increase than adding more armor.
Can this tool be used for all champion builds?
Yes, this calculator is universal and works for any champion in the game. Because the defensive math in League of Legends is static and applies consistently across all characters, you only need to input your current Health and Armor stats to receive an accurate EHP output. Whether you are playing a high-health tank or a squishy damage dealer, the defensive math remains the same. You can use this tool to compare different item combinations before you return to the base, ensuring you maximize your combat efficacy for the next team fight.
Does this calculator save my data?
This tool is designed with a strict privacy-first approach and does not save any user data. It does not use cookies, local storage, indexedDB, or server-side databases. All calculations are performed entirely in your browser's active memory. Because the application is stateless, every calculation is wiped when you refresh or close the page. This ensures that no personal preferences or build history are tracked, providing a clean, secure, and ephemeral experience for every session.
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