Math

Probability Calculator

Built by Kevin Glover · @gloverbuilds · Verified formula

P(A and B), P(A or B), and conditional probability for any two events.

📅 Updated April 2026 ✅ Formula verified 📖 4 min read 🆓 Free · No sign-up

In this article

Independent vs dependent events
The addition rule
Real-world examples

Probabilidade entre 0 (impossível) e 1 (certo). Regras: complementar (1-P), adição (P(A)+P(B)-P(A e B)), multiplicação para independentes (P(A)×P(B)). Na Mega-Sena, chance de acertar 6 = 1 em 50 milhões.

Probabilidade é cobrada regularmente no ENEM e em concursos de áreas quantitativas.

⚡ CalcWolf Insight

The birthday paradox: in a group of just 23 people, there is a 50% chance that two people share the same birthday.

Frequently asked questions

Chance de ganhar na Mega-Sena?▾

1 em 50.063.860 para a sena. Quadra: 1 em 2.332. Quina: 1 em 154.518.

Eventos independentes?▾

P(A e B) = P(A) × P(B). Cara em duas moedas: 0,5 × 0,5 = 25%.

O que é probabilidade condicional?▾

P(A|B) = P(A e B) / P(B). Probabilidade de A dado que B já ocorreu.

Cai no ENEM?▾

Sim, regularmente. Eventos simples, compostos, combinação e análise combinatória.

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Kevin Glover · @gloverbuilds

Founder, CalcWolf · GLVTS · Blickr

All formulas sourced from primary references — IRS publications, peer-reviewed research, and official standards. Results are tested against independent reference calculators before publishing. Rates and brackets updated when official sources change. Editorial policy →