Calculadora de risco de gravidez por dia do ciclo
Calcule o risco de gravidez de uma relação concreta a partir das datas do seu ciclo. Usa a janela fértil de seis dias estabelecida por Wilcox (NEJM 1995) e mostra uma faixa de risco em vez de uma percentagem inventada.
How to use this calculator
- Enter the first day of your last period — the day bleeding started, not when it ended.
- Enter your usual cycle length. If it varies a lot, tick the irregular box: the calculator will tell you it cannot estimate rather than guess.
- Enter the date of the encounter and the contraception in use.
- Read the band, not a percentage. Day-specific probabilities are only published for two days of the window, so inventing a number for the rest would be dishonest.
FAQ
How many days of the cycle carry real pregnancy risk?
Six: the five days before ovulation and the day of ovulation itself. In the Wilcox study (NEJM, 1995), covering 221 women and 625 cycles, no conception occurred from intercourse outside that window.
What is the probability on each day?
The study publishes figures for two days: 10% five days before ovulation and 33% on the day of ovulation. No point estimates are published for the days in between, so this calculator shows a band instead of inventing a number.
What if my cycles are irregular?
Then ovulation cannot be placed reliably, and the calculator says so explicitly. The luteal phase is fairly stable at about 14 days, but that only helps if you know when the next period will start.
Does the method failure rate add to the cycle-day risk?
No, and combining them is a common mistake. Condom or pill failure rates are annual figures for a year of continuous use. The cycle-day risk is for one specific encounter. They are different quantities and must not be multiplied together.
CalcVita. (2026). Calculadora de risco de gravidez por dia do ciclo. CalcVita. Retrieved 31 de julho de 2026, from https://calcvita.com/pt/calculadoras/risco-de-gravidez