Probability Calculator

Calculate probability from favorable and total outcomes. Find combined probability for independent or mutually exclusive events.
Mode

Probability

30.00%

Fraction

3/10

Odds

3 to 7

Probability Details

P(Event)0.3000
P(Not Event)0.7000
As Fraction3/10
As Percentage30.00%
As Decimal0.300000
Odds (for : against)3 to 7

Use the Probability Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Our Probability Calculator simplifies the process of determining the likelihood of events. Whether you're analyzing the 2026 global economic forecast where there's a 70% chance of moderate growth according to the IMF, or assessing the probability of your startup securing funding from the 50,000 venture capital firms projected to be active in 2026, this tool provides quick and accurate results. It's essential for anyone making data-driven decisions, from business strategists to students.

This calculator uses fundamental probability formulas. For a single event, probability (P) is calculated as P = (Number of Favorable Outcomes) / (Total Number of Possible Outcomes). For independent events A and B, the combined probability P(A and B) = P(A) * P(B). For mutually exclusive events A and B, the combined probability P(A or B) = P(A) + P(B).

Ensure your outcomes are truly 'favorable' and 'total' for accurate single-event probability calculations. When dealing with combined probabilities, carefully distinguish between independent events (where one doesn't affect the other) and mutually exclusive events (where both cannot occur simultaneously). A common mistake is using the independent events formula for mutually exclusive events, leading to incorrect results.

Example: 2026 Tech Investment Success

  1. 1 You are launching a new AI-powered educational platform in 2026. There are 10 major venture capital firms specializing in EdTech, and you've secured meetings with 3 of them. Additionally, there's a 60% chance that the overall EdTech market will grow by over 15% in 2026, a separate, independent factor influencing your success.
  2. 2 First, calculate the probability of securing funding from one of the 3 firms: 3 (favorable) / 10 (total) = 0.3 or 30%. Then, calculate the combined probability of securing funding AND the market growing by over 15%: P(funding) * P(market growth) = 0.3 * 0.6 = 0.18.
  3. 3 The probability of securing funding from one of the 3 target firms is 30%. The combined probability of securing funding AND the EdTech market growing by over 15% in 2026 is 18%.
  4. 4 This 18% combined probability represents a more realistic outlook for your startup's success, considering both your direct efforts and the broader market conditions. This type of analysis helps in setting realistic expectations and planning for contingencies in the competitive 2026 tech landscape.

Source: Khan Academy · Last updated: April 2026

Frequently Asked Questions

How do you calculate the probability of two events happening?
For independent events, multiply their individual probabilities. For example, the probability of flipping heads twice in a row is 1/2 times 1/2 = 1/4 or 25%.
What is the difference between independent and mutually exclusive events?
Independent events do not affect each other (like two coin flips). Mutually exclusive events cannot happen at the same time (like rolling a 3 and a 5 on one die). For mutually exclusive events, add their probabilities.
How do you calculate odds from probability?
Odds in favor equals probability divided by (1 minus probability). If the probability is 0.25 (25%), the odds are 0.25/0.75 = 1:3, meaning 1 favorable outcome for every 3 unfavorable.

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