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⏱️ Essential Mage Tool

Cooldown Reduction Calculator

Calculate your cooldown reduction, ability haste, and final spell cooldowns. Perfect for League of Legends, Dota 2, WoW, and all MOBA/RPGs. Optimize your ability uptime.

⏱️ Calculate Cooldown Reduction

📋 Quick Build Presets

🛡️ Common CDR Items

Cosmic Drive
Ability Haste +30
Black Cleaver
Ability Haste +30
Axiom Arc
Ability Haste +25
Ionian Boots
Ability Haste +15

Your Results

Effective CDR
0.00%
Very Low
Minimal impact
Final Cooldown
10.00s
Reduced by 0.00s
Casts Per Minute
6.0
Maximum ability usage
Buff Uptime (10s duration)
100.0%
5s buff: 50.0%
15s buff: 100.0%

🎯 Next Breakpoints

10% CDR +11 Haste
Need 11 total Haste
20% CDR +25 Haste
Need 25 total Haste
30% CDR +43 Haste
Need 43 total Haste
💡 PRO TIP

Consider adding more CDR items. You're at very low CDR.

Understanding Cooldown Reduction

What is Cooldown Reduction?

Cooldown Reduction (CDR) is a stat that decreases the time between ability casts. It's expressed as a percentage and directly reduces your ability cooldowns, allowing you to cast spells more frequently.

Classic CDR Formula

Final Cooldown = Base Cooldown × (1 - CDR%)

Example: 10s cooldown with 40% CDR = 10 × (1 - 0.40) = 6 seconds

Ability Haste Formula (LoL)

Effective CDR% = Ability Haste / (Ability Haste + 100)

Example: 100 Ability Haste = 100 / (100 + 100) = 50% effective CDR

Why Ability Haste?

Ability Haste scales linearly, meaning each point is equally valuable. This prevents CDR-stacking from being overpowered and makes itemization choices more flexible.

CDR Value by Percentage

10% CDR
10s becomes 9s
Minimal
+11% more casts
20% CDR
10s becomes 8s
Noticeable
+25% more casts
30% CDR
10s becomes 7s
Good
+43% more casts
40% CDR
10s becomes 6s
Excellent
+67% more casts
50% CDR
10s becomes 5s
Very High
+100% more casts

When CDR Matters Most

✓ High Priority For:
  • Mages and spellcasters
  • Support champions
  • Ability-based assassins
  • Tanks needing CC uptime
  • Champions with low base CDs
✗ Low Priority For:
  • ADCs and marksmen
  • Auto-attack carries
  • One-shot burst builds
  • Resource-limited champions
  • Split-push specialists

CDR vs Ability Haste Comparison

Classic CDR (Old System)
  • Percentage-based reduction
  • Diminishing returns at high values
  • 40% was often the sweet spot
  • Going from 30% to 40% was very valuable
  • Used in most MOBAs and older games
Ability Haste (Modern System)
  • Flat stat that converts to CDR
  • Linear scaling - no diminishing returns
  • Every point equally valuable
  • 100 Haste = 50% effective CDR
  • Used in League of Legends (S11+)
📊 CONVERSION TABLE
30 Haste
≈ 23% CDR
60 Haste
≈ 38% CDR
100 Haste
= 50% CDR
200 Haste
≈ 67% CDR

CDR Build Strategies

🔮

Burst Mages

Moderate CDR (20-30%) is enough for burst combos. Focus on ability power and penetration first, then add CDR for team fights.

  • Priority: AP > Magic Pen > CDR
  • Target: 25-35% CDR
  • One rotation should secure kills

Battle Mages

High CDR (40-50%) for sustained DPS. Spam abilities in extended fights. Balance with mana/energy management.

  • Priority: CDR = AP > Survivability
  • Target: 40-50% CDR
  • Need mana regen or large mana pool
🛡️

Tanks

Moderate to high CDR (30-40%) for CC chains and peel. More CC uptime means better frontline control.

  • Priority: Resistances > Health > CDR
  • Target: 30-40% CDR
  • Many tank items provide CDR
💚

Enchanters

Maximum CDR (45-50%) for constant healing and shielding. Your team's survivability scales with your CDR.

  • Priority: CDR > Mana Regen > AP
  • Target: 45-50% CDR
  • Rush CDR items early

Frequently Asked Questions