How to Calculate Probability

If you want to know how to calculate probability, then you must first relax because you have found the right article to teach you just that.

How To Calculate Probability
How To Calculate Probability

Probability is a math tool used in different situations. Like when you guess how sales will go up, or when you figure out the likelihood of getting new customers from a marketing plan. It’s also handy for guessing the chance of stuff happening.

In this article, we’ll explore everything about probability and how to calculate it for different events. We’ll also see how it’s different from the odds.

What is Probability?

Probability is how likely something will happen. It shows the chance of getting a specific result and can be figured out using a basic formula.

You can also think of probability as the chance of an event happening compared to all the possible outcomes. When there are many events, you calculate each one separately and then multiply the results to find the overall chance of a certain outcome.

Formula for Probability

The probability formula shows how likely an event will occur. To find the probability of an event, you compare the number of ways it can happen to all possible outcomes. Probabilities are always between 0 and 1. The basic probability formula is:

Probability = Number of ways an event can happen / Total number of possible outcomes


P(A) = f / N


P(A) = Probability of an event (event A) happening.

f = Number of times an event can occur (frequency)

N = Total number of possible outcomes

How to calculate the probability 

Probability calculations involve basic multiplication and division to analyze potential results of events, like introducing new products, reaching out to bigger groups of people, or creating a fresh approach to generating leads.

A step-by-step process to find the probability of a single event.

Here’s how to find out a single-event probability:

Pick one event you want to find the probability of.

To solve a probability problem, first, choose what probability you want to calculate. This could be something like the probability of rain on a Wednesday or getting a certain number when you roll a dice. The thing you pick should have at least one way it could turn out.

For instance, if you want to know the probability of getting a “3” when you roll a die, you’d know there’s one good way: rolling a “3.”

Identify the total number of outcomes that can happen

Next, figure out how many different results could come from the event you chose in step one. For rolling a dice, there are six different numbers, so that’s how many possible things could happen. So if you’re looking at getting a “3” on the first roll, there could be six different things that could happen.

Divide the number of events by all the possible outcomes

Once you know the event you’re thinking about and its corresponding outcomes, divide the number of ways that event can happen by the total number of possible outcomes. Rolling the dice once and getting a “3” is one way.

You can keep rolling the dice and counting the outcomes. Every time you roll is like one situation. So for this dice example, divide one situation by the six possible outcomes that could happen:

  • This gives you a fraction: 1/6.
  • That means the probability you’ll roll a “3” on the first try is one out of six.

A step-by-step process for calculating the probability of multiple events

The formula for calculating the probability of two events happening is:

P(A and B) = P(A) x P(B)


  • P(A and B) = Probability of both A and B events occurring
  • P(A) = Probability of event A
  • P(B) = Probability of event B

Calculating probability for multiple random events is like doing it for just one event, but there are more steps. To find the chance of two events happening together, like rolling two dice and getting a “6” on both, follow these steps:

Pick the events you’ll calculate

First, choose the events you want to find the probabilities of. For example, if you’re looking at rolling two dice and getting “6” on both, each die’s roll is an event.

Calculate each event’s probability

Next, calculate the probability of rolling “6” on each die. It turns out to be a 1 in 6 chance for each die.

Using these results, you can then find the total probability of these two events occurring simultaneously.

Multiply the probabilities together

Finally, multiply the probability you calculated earlier to get the total probability of both events happening at once. In the dice example, you’d multiply the 1/6 chances:

  • Total chance = 1/6 x 1/6 = 1/36
  • So, there’s a 1 in 36 chance of rolling “6” on both dice at the same time.


What are the Types of probability?

The four types of probability include:

  • Classical
  • Empirical
  • Subjective
  • Axiomatic

What is the addition rule of probability?

The addition rule states that for two mutually exclusive events A and B, the probability of A or B occurring is P(A or B) = P(A) + P(B).

What is the multiplication rule of probability?

The multiplication rule states that for two independent events A and B, the probability of A and B both occurring is P(A and B) = P(A) * P(B).

What is conditional probability?

Conditional probability is the probability of one event happening given that another event has already occurred. It’s denoted as P(A|B) and calculated as P(A and B) / P(B).

How do I calculate the probability of complementary events?

The probability of an event A not occurring (complement of A) is 1 minus the probability of A occurring: P(not A) = 1 – P(A).



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