Coincidence Probability Calculator
Calculate the mathematical probability of coincidences and seemingly impossible events
The Mathematics of Coincidences
🧮 Calculation Method
Our calculator considers multiple factors:
- Base Probability: P(A) × P(B) for independent events
- Multiple Trials: 1 - (1-p)^n formula
- Population Effect: More people = more chances
- Time Window: Longer periods increase probability
🎯 Common Fallacies
People often misjudge coincidences because of:
- Post-hoc reasoning: Calculating odds after the event
- Ignoring opportunities: Not counting all chances
- Confirmation bias: Remembering hits, forgetting misses
- Vague definitions: Expanding what counts as a "match"
🎂 The Birthday Paradox
The famous birthday paradox illustrates how coincidences are more likely than we think. With just 23 people in a room, there's a 50% chance two will share a birthday. With 50 people, it's 97%! This happens because we compare everyone to everyone else, creating many opportunities for matches.
Famous Coincidences Analyzed
Lincoln-Kennedy Coincidences
Probability: ~0.001%
Reality: Cherry-picked facts ignore non-matches
Meeting Friend Abroad
Probability: ~0.1-1%
Reality: Popular destinations make this likely
Thinking of Someone Before Call
Probability: ~5-10%
Reality: We think of many people daily
🎲 Types of Independence
Independent Events
One event doesn't affect the other's probability. Examples: lottery numbers, coin flips.
Related Events
Events share some common factors but aren't directly connected. Example: meeting someone at an event.
Dependent Events
One event directly influences the other's probability. Example: rain and umbrella sales.
🔗 Continue Your Analysis
Explore more aspects of unusual events: