Emergency contraception timing

Enter the time of unprotected sex and see how much of each recommended window is left.

Time of unprotected sex

WHO note: the sooner, the more effective.

Levonorgestrel
Within 72 hours
Available
Time remaining3d 0h left
Ulipristal acetate
Within 120 hours
Available
Time remaining5d 0h left
Copper IUD
Insertion within 120 hours
Available
Time remaining5d 0h left

Based on WHO and FDA timing recommendations (LNG 72h, UPA and copper IUD 120h). Learn more
For reference only. Prescription rules and availability differ by country. Talk to a pharmacist or doctor.

How does it work?

Emergency contraception works best the sooner it is taken after intercourse. Three options:

  • Levonorgestrel (LNG, "Plan B"): within 72 hours (3 days) — 95% effective at 24 h, 85% at 25-48 h, 58% at 49-72 h.
  • Ulipristal (UPA, "Ella"): within 120 hours (5 days), maintains effectiveness later than LNG.
  • Copper IUD: insertion within 120 hours, 99% effective — the strongest option.

The main mechanism is delaying or blocking ovulation; emergency contraception does not end an already-implanted pregnancy (it is not an abortifacient).

Limitations

Emergency contraception has known limits:

  • Weight: LNG effectiveness drops at BMI > 26 or weight > 70-75 kg; UPA drops at BMI > 35 or > 88-90 kg (FDA/WHO data).
  • If ovulation has already happened, both LNG and UPA are less effective.
  • It does not protect against further unprotected sex in the same cycle.
  • Frequent use (more than once a month) is not recommended — switch to regular contraception.
  • Use with caution in severe asthma or liver disease.

If your next period is more than 1 week late, take a pregnancy test.

Sources

Frequently asked

Which emergency contraception is most effective?

A copper IUD is the most effective option at 99%, but it requires insertion. Among pills, UPA (Ella) maintains better effectiveness up to 5 days than LNG (Plan B).

LNG is the most accessible (over-the-counter in many places) but is effective only within 72 hours and is affected by weight. Whichever option, the sooner the better — within 24 hours gives the highest effectiveness.

What if I might still be pregnant after using emergency contraception?

If your period is more than 1 week late, or is unusually light, take a pregnancy test. Light bleeding after emergency contraception is common but is not a true period.

If the test is positive, see your OB-GYN to start regular prenatal care — emergency contraception does not affect an already-implanted pregnancy.