Trying to understand your odds of pregnancy while on the pill? Get a quick, baseline estimate in seconds.
* Calendar dates cannot identify a safe day on the combined pill. This is an approximate per-act estimate, not a probability for a specific missed-pill episode. If pills were missed, follow the instructions for your pill or ask a pharmacist.
How to use this for pill users
- Select your pill type: combined pill or progestin-only pill (mini-pill).
- Choose perfect if it was taken exactly as directed with no lapses; choose typical if there were any slip-ups, late starts, condom issues, or uncertainty.
- Optionally add a second method (e.g., condoms) to see how it changes the risk.
Have specific misses or late pills? Get a tailored result with the Missed Pill Pregnancy Risk Calculator.
What changes your chances on the pill
- Timing and consistency: Taking pills at the same time each day matters—especially for the mini-pill.
- Missed/late pills: Multiple misses or a late restart after the hormone-free break raises risk (use the missed-pill tool above).
- Vomiting/diarrhea: Within a few hours of a dose can prevent absorption.
- Certain medicines/supplements: Rifampin-like antibiotics, some seizure meds, and St. John’s wort can reduce effectiveness. Check with a clinician or pharmacist if unsure.
- Backup and stacking: Using condoms as well reduces the chance of pregnancy further and protects against STIs.
Annual failure rates are very low with perfect use (around 1 in 300) and higher with typical use (several in 100). The calculator gives an approximate per-act estimate, but bleeding dates cannot predict a safe day on the pill.
If you had a slip-up
If you missed pills, started a new pack late, or had vomiting/diarrhea close to a dose, consider emergency contraception (EC). Compare timing and options with the Emergency Contraceptive Pill Effectiveness Calculator, then follow the instructions on when to resume/continue your pill and whether to use backup.
When to take a pregnancy test
Most people get a reliable result from the first missed period. To see accuracy by day, use the Pregnancy Test Accuracy Calculator.
Methodology
The combined pill suppresses ovulation when used correctly. Bleeding dates do not reveal a natural fertile window on the pill, so this calculator does not raise or lower the estimate by predicted cycle day. Date and cycle inputs are retained as encounter context, not as evidence of protection.
The per-act model uses your typical/perfect-use selection, optional additional methods and personal inputs. It does not calculate the risk from a specific missed pill, late pack, interaction or absorption problem. Follow the relevant CDC guidance on combined hormonal contraception and missed pills or ask a pharmacist for those situations.
Annual contraceptive failure rates are not per-encounter probabilities. Converting them and adjusting for personal factors requires assumptions; the displayed percentage is approximate. The model includes typical/perfect use and additional methods; results are capped at 40%.
Important
This page estimates risk using published effectiveness data and your inputs. It does not diagnose or replace care from a clinician.