Pregnancy Test Calculator

The timing of a pregnancy test matters significantly for accuracy. Home pregnancy tests detect human chorionic gonadotropin (hCG), a hormone produced after a fertilized egg implants in the uterus. hCG levels rise rapidly in early pregnancy, doubling approximately every 48-72 hours, but they start at very low levels that may not be detectable immediately.

For the most reliable results, wait until after you have missed your period. Testing on the first day of your missed period gives you about 99% accuracy with most home pregnancy tests. Testing earlier is possible — some sensitive tests claim to work up to 6 days before your missed period — but the accuracy drops significantly. At 6 days early, accuracy is only about 62%, rising to about 90% at 2 days before your missed period.

Blood tests performed at your doctor's office can detect pregnancy earlier than urine tests, sometimes as early as 6-8 days after ovulation. There are two types: qualitative blood tests (yes or no) and quantitative blood tests (exact hCG level). If you get a negative result but still suspect you are pregnant, wait a few days and test again, or see your healthcare provider for a blood test.