Last Updated: 3/10/2026

How to Use the Calculator

Interface Overview

The calculator features a simple interface with five input parameters and a dynamic probability chart. All inputs update the chart in real-time.

Input Parameters

1. Desired Unit Cost (1-5)

What it means: The cost tier of the champion you’re looking for.

• 1-cost: Common units (e.g., basic carries and support units)
• 2-cost: Uncommon units
• 3-cost: Rare units (often key carries)
• 4-cost: Epic units (premium carries and supports)
• 5-cost: Legendary units (game-changing champions)

How to set: Use the slider to select 1, 2, 3, 4, or 5.

2. Current Level (1-11)

What it means: Your summoner level, which determines shop odds for each cost tier.

Why it matters: Higher levels dramatically increase the odds of seeing higher-cost units:

• Level 1-2: Only 1-cost units
• Level 3-4: Mostly 1-cost, some 2-cost
• Level 5-6: Mix of 1-3 cost
• Level 7-8: Balanced distribution, 4-costs appear
• Level 9+: High-cost units become common

How to set: Use the slider to select your current level (1-11).

Pro Tip: If you’re planning to level up before rolling, set this to your target level, not your current level.

3. Number of Copies Already Out

What it means: How many copies of your specific unit are already on boards or benches (including yours).

Why it matters: Each unit has a limited pool size:

• 1-cost: 22 copies total
• 2-cost: 20 copies total
• 3-cost: 17 copies total
• 4-cost: 10 copies total
• 5-cost: 9 copies total

How to set: Enter a number in the text field.

Example: You’re looking for Ahri (3-cost). You have 2 copies, and you’ve seen 3 more on other boards. Enter 5.

Tracking Tips:

• Count your own copies
• Watch for contested units during carousel
• Note when opponents sell units (they return to pool)
• Use scouting to track popular units

4. Number of Units of Same Cost Already Out

What it means: Total number of units of the same cost tier that are out of the pool (all champions of that cost).

Why it matters: This affects the denominator in the probability calculation. The pool is shared across all champions of the same cost.

How to set: Enter a number in the text field.

Example: You’re rolling for a 3-cost unit. If you estimate roughly 30 total 3-cost units are on boards across all players, enter 30.

Estimation Guide:

• Early game (Stage 2-3): Relatively few units out
• Mid game (Stage 4-5): Moderate depletion
• Late game (Stage 6+): Heavy depletion, especially for contested costs

Quick Math:

• Total pool for cost tier = Bag size × Distinct champions
• 3-cost example: 17 × 13 = 221 total 3-cost units

5. Amount of Gold to Roll

What it means: How much gold you plan to spend rerolling.

Why it matters: More gold = more shops = higher probability of hitting your unit.

How to set: Enter a number in the text field (typically 10-80).

Standard Roll Amounts:

• 10-20 gold: Light roll, checking for upgrades
• 30-40 gold: Standard roll down
• 50-60 gold: Heavy roll down (all-in)
• 70+ gold: Desperation rolling

Note: Each 2 gold = 1 reroll = 5 shops

Reading the Results

The Probability Chart

The chart displays a bar graph with:

• X-axis: Number of copies (1-9)
• Y-axis: Probability (0-1 or 0%-100%)
• Bars: Show the probability of getting at least X copies

Interpreting Probabilities

Example Reading:

• Bar at “3” shows 0.65 → You have a 65% chance of hitting at least 3 copies
• Bar at “6” shows 0.15 → You have a 15% chance of hitting at least 6 copies

What Probability is “Good”?

Hover for Details

Hover over any bar to see the exact probability value.

Practical Examples

Example 1: Finding Your 3-Cost Carry

Scenario: Level 7, looking for Ahri to complete your 3-star.

Inputs:

• Desired unit cost: 3
• Current level: 7
• Copies already out: 6 (you have 6 Ahri)
• Same cost units out: 40 (estimated)
• Gold to roll: 40

Result: Check the bar at “3” (need 3 more for 3-star). If it shows 75%, you have a good chance!

Example 2: Contested 4-Cost

Scenario: Level 8, two players are running the same 4-cost carry.

Inputs:

• Desired unit cost: 4
• Current level: 8
• Copies already out: 8 (heavily contested)
• Same cost units out: 50
• Gold to roll: 50

Result: Lower probability due to competition. Might want to pivot if odds are poor.

Example 3: 5-Cost Hunting

Scenario: Level 9, looking for that game-winning 5-cost.

Inputs:

• Desired unit cost: 5
• Current level: 9
• Copies already out: 0 (uncontested)
• Same cost units out: 10
• Gold to roll: 60

Result: Even with 60 gold, 5-costs are rare at level 9. Consider if level 10 would be better.

Common Mistakes to Avoid

1. Forgetting to Update Level

Always set the level to where you’ll be WHEN rolling, not where you are now.

2. Underestimating Pool Depletion

In late game, many units are out. Don’t use 0 for the pool depletion field.

3. Misunderstanding “At Least”

The probabilities show “at least X copies,” not “exactly X copies.”

4. Ignoring Headliners

The calculator accounts for headliners automatically, but remember that headliner shops reduce your effective number of shops.

5. Not Accounting for Sold Units

If an opponent sells units, they return to the pool, improving your odds.

Tips for Optimal Use

Pre-Roll Planning

Run calculations BEFORE committing to a roll down. This helps you decide:

• Should I roll now or level first?
• Do I have enough gold for reasonable odds?
• Is this unit too contested?

Live Adjustments

Keep the calculator open during games and update values as you see more information about pool depletion.

Probability Thresholds

Set personal thresholds (e.g., “I only roll if I have 70%+ chance”) to maintain discipline.

Compare Scenarios

Run multiple calculations:

• Level 7 with 40 gold vs. Level 8 with 30 gold
• Contested unit vs. uncontested alternative

Advanced Usage

Accounting for Headliners

The calculator automatically includes headliner probabilities based on your level and the unit cost. Headliners give you 3 copies instead of 1, significantly improving your odds.

Multiple Roll Downs

If planning multiple roll downs (e.g., one at 3-2, another at 4-2), run separate calculations for each.

Probability Chains

For complex scenarios (e.g., “what if I roll 20 gold, and if I don’t hit, roll 30 more?”), you’ll need to chain probabilities manually.

Next Steps

• Mathematical Background: Understand the math behind the calculations
• Game Mechanics Reference: Detailed TFT shop mechanics
• Technical Implementation: For developers interested in the code