Last Updated: 3/10/2026

Game Mechanics Reference

Overview

This document provides detailed information about Teamfight Tactics game mechanics relevant to rolling calculations. All data is current as of Set 10.

Unit Pool Mechanics

Bag Sizes (Set 10)

Each champion has a limited number of copies in the shared pool:

Pool Sharing

The unit pool is shared across all players:

• When any player purchases a unit, it’s removed from the pool
• When a player sells a unit, it returns to the pool
• Units on benches and boards are out of the pool
• Dead units (from eliminated players) remain out of the pool

Star Level Requirements

Example: To create a 3-star unit, you need to find 9 copies total (which combine into three 2-stars, then one 3-star).

Shop Odds by Level

Standard Shop Probabilities

The probability of each cost appearing in a shop slot varies by level:

Key Breakpoints

Level 3: First level where 2-costs appear (25% chance)

Level 5: First level where 4-costs appear (2% chance)

Level 7: First level where 5-costs appear (1% chance)

• Balanced distribution for 2-cost and 3-cost (35% each)
• Common level for rolling down for 3-cost carries

Level 8:

• Best level for finding 3-cost units (36% chance)
• Reasonable 4-cost odds (18%)
• Most versatile level for rolling

Level 9:

• Best level for 4-cost units (35% chance)
• Significant 5-cost appearance (10%)
• Standard level for late-game carries

Level 10:

• Optimal for 4-cost units (40% chance)
• Good 5-cost odds (25%)

Level 11:

• Best for 5-cost units (35% chance)
• Excellent 4-cost odds (50%)
• Very rare to reach in normal games

Headliner Mechanics

What are Headliners?

Headliners are special shop offerings (Set 10 mechanic) that:

• Appear as a full shop of 5 units from the same trait
• Give 3 copies of the chosen unit instead of 1
• Have increased star level (+1 star)
• Cannot appear in consecutive shops (4-shop cooldown)

Headliner Probabilities

The probability of a headliner shop appearing varies by level and cost:

Note: After getting a headliner, the next 4 shops cannot be headliners.

Impact on Calculations

Headliners significantly improve odds because:

1. They give 3 copies instead of 1
2. They effectively “skip” 2 states in the Markov chain

The calculator accounts for:

• Probability of getting a headliner on each shop
• The 4-shop cooldown after a headliner
• The 3-copy jump in the state transition

Rolling Mechanics

Shop Refresh

• Cost: 2 gold per reroll
• Shops per reroll: 5 unit slots
• Shops per gold: 2.5 shops per gold spent

Example: 40 gold = 20 rerolls = 100 shops

Shop Generation Process

1. For each of the 5 slots: a. Roll for cost tier (based on level) b. Roll for specific champion (uniform among remaining champions of that cost) c. Check for headliner eligibility

2. Pool depletion is immediate: If you buy a unit, it’s removed before the next shop

Lock Mechanic

Players can “lock” their shop:

• Costs 0 gold
• Preserves current shop when leveling or waiting
• Units are still out of the pool while locked
• Doesn’t affect rolling calculations

Strategic Implications

Contested Units

When multiple players want the same unit:

• Pool depletes faster
• Odds decrease for everyone
• Earlier rolling has advantage

Example: If 3 players are rolling for the same 4-cost carry:

• Pool of 10 copies
• Each player getting 3 copies means only 1 left
• Last player has very poor odds

Level vs. Roll Decision

Leveling Advantages:

• Better odds for higher-cost units
• More board strength immediately
• Better economy in long run

Rolling Advantages:

• More shops for current odds
• Can hit units before others
• Cheaper (2 gold per roll vs. 4+ for levels)

Break-even Analysis:

• Level 7→8 costs 24 gold
• That’s 12 rerolls = 60 shops at level 7
• Compare: 36% chance at level 8 vs. 35% × 60 shops at level 7

Optimal Rolling Levels

For 1-cost: Level 3-5

• Highest odds, but usually not worth rolling for

For 2-cost: Level 5-6

• 33-40% odds
• Common for early reroll comps

For 3-cost: Level 7-8

• 35-36% odds
• Standard carry level
• Most common roll-down timing

For 4-cost: Level 8-9

• 18-35% odds
• Level 9 strongly preferred
• High-roll territory at level 8

For 5-cost: Level 9-10+

• 10-25% odds
• Usually need level 10+ for reasonable odds
• Very expensive to roll for

Economy Considerations

Gold Generation

• Base: 5 gold per round
• Interest: +1 gold per 10 gold saved (max +5 at 50 gold)
• Win/Loss Streak: +1 to +3 gold
• Total: Typically 6-13 gold per round

Rolling Costs

Common Roll Timings

Stage 3-2 (Krugs):

• ~30-40 gold available
• Level 6-7
• Rolling for 2-cost or 3-cost carries

Stage 4-1/4-2:

• ~50-60 gold available
• Level 7-8
• Main roll-down timing for 3-cost carries

Stage 4-5/5-1:

• ~60-80 gold available
• Level 8-9
• Rolling for 4-cost carries or 3-star 3-costs

Stage 5-5+:

• Variable gold
• Level 9-10
• Desperation rolling or 5-cost hunting

Set-Specific Considerations

Set 10 Updates (as of 26/11/23)

Bag Size Changes:

• 1-cost: 22 copies (was 29)
• 2-cost: 20 copies (was 22)
• 3-cost: 17 copies (was 18)
• 4-cost: 10 copies (was 12)
• 5-cost: 9 copies (was 10)

Impact:

• Higher-cost units are more contested
• 3-starring 4-costs and 5-costs is harder
• Pool depletion matters more

Distinct Champions:

• All costs have 13 distinct champions except 5-cost (8 champions)
• More diverse pool than some previous sets

Historical Context

Previous sets had different bag sizes. If using this calculator for older sets, you would need to update the constants in the code:

const totalUnits = [22, 20, 17, 10, 9];  // Set 10
const distinctChamps = [13, 13, 13, 13, 8];  // Set 10

Advanced Mechanics

Shop Uniqueness

Within a single shop (5 units), you cannot see:

• The same champion twice (unless one is a headliner)
• Exception: Different star levels of the same champion can appear

Carousel Priority

Carousel units:

• Are removed from the pool while on carousel
• Return to pool if not picked
• Don’t affect shop odds during carousel round

Selling Units

When selling units:

• They immediately return to the pool
• Other players can find them in their next shop
• Useful for “passing” units in coordinated play

Probability Edge Cases

Zero Units Left

If all copies of a unit are out:

• Probability becomes 0
• Shop cannot generate that unit
• Calculator handles this with Math.max(0, ...)

Pool Exhaustion

If an entire cost tier is exhausted:

• Game rerolls for a different cost
• Very rare in practice
• Calculator assumes this doesn’t happen

Headliner Conflicts

If a headliner would give you a unit that’s exhausted:

• Headliner doesn’t appear
• Normal shop is generated instead
• Probability calculations remain valid

Next Steps

• How to Use: Apply these mechanics practically
• Mathematical Background: Understand the probability math
• Technical Implementation: See how this data is used in code