The pregnancy test calculator can help you calculate the best time to take a regular pregnancy test or a specially marked early pregnancy test.
How Pregnancy Tests Work
Pregnancy tests work by measuring or detecting the level of human chorionic gonadotropin (hCG) in a woman's urine or blood. Home pregnancy tests are generally urine sticks which detect if hCG is present in urine. A pregnancy blood test detects if hCG is present in the blood. A doctor will generally not order a blood test until you have missed a period.
HCG is short for Human chorionic gonadotropin, a hormone produced by the placenta during pregnancy.
Two Types of Home Pregnancy Tests
Tests offer different accuracies and sensitivities but can basically be divided into two categories: early and regular.Early home pregnancy tests: Early home pregnancy tests are more sensitive than regular tests so can be used even before a period is missed. However, some accuracy is sacrificed by testing early. Early tests will normally be clearly labeled and marketed as early pregnancy tests.
Regular home pregnancy tests: Regular home pregnancy tests are only effective from the day a period is missed.
Purchasing Pregnancy Tests
Home pregnancy tests are not all equal. Here's what to look out for when purchasing a pregnancy test:
Accuracy: Accuracy measurements are expressed as percentages and most home tests claim 99% accuracy. Importantly, manufacturers normally state that their accuracy measurements are only valid if the test is performed from the day of your first missed period and only if hCG is present.
Sensitivity: Sensitivity is the range of hCG the pregnancy test can detect. As with accuracy, you can usually find the sensitivity of a pregnancy test on its packaging. Sensitivity is measured in milli-international units per milliliter, usually abbreviated to mIU/ml. The lower the mIU per ml, the greater the ability of the test to detect hCG. Tests with low mIU are commonly labeled early pregnancy tests since they can detect smaller amounts of hCG.
Most pregnancy tests available at a drug or grocery store are perfectly fine for testing after a missed period, otherwise see here on early tests.
How Soon Can You Take A Pregnancy Test?
An early home pregnancy test can be taken up to 5 days before a woman's expected menstrual period is due. A positive early pregnancy test result will be reasonably accurate and reliable. However a negative early pregnancy test result can be very unreliable as the hCG concentrations are still low and need time to increase.
Early pregnancy tests are more sensitive (lower mIU/ML) than regular tests, so they are better able to detect hCG, but since every woman is different, it is possible that the level of hCG present in an individual woman's urine may not be high enough for a particular test to detect.
Medications are also known to affect pregnancy test results and can produce false negatives and false positives.
When is the Earliest Time to Take an Early Home Pregnancy Test?
As women all have different ovulation and menstrual cycles, if you know the date you ovulated and the average length of your menstrual cycle it can help you choose the day to take an early pregnancy test.
9 to 11 days after ovulation (9dpo - 11dpo)
5 to 4 days before your expected period
DPO = Days Past Ovulation
12 to 13 days after ovulation (12dpo - 13dpo) or
1 to 2 days before your expected period
DPO = Days Past Ovulation
When is the Best Time to Take A Home Pregnancy Test for Greatest Accuracy?
From 14 to 15 days after ovulation (14dpo - 15dpo) or
From the day of your expected period or soon after
DPO = Days Past Ovulation
Early Pregnancy Test Accuracy
Pregnancy test manufacturers give accuracies based on a woman ovulating/conceiving 14 days before her expected period. Also assumed is that each woman taking a pregnancy test knows the date her expected menstrual period is due or the length of her menstrual cycle. Both these variables can he highly irregular and affect how soon hCG is detectable.
HCG starts being detectable in urine with its lowest accuracy at approximately 8 days after ovulation/conception. Accuracy is highest from 14 days after ovulation/conception which is commonly the day of the expected period for women with regular cycles.
Best Overall Time to Test
Since most pregnancy test manufacturers claim highest accuracy from the day of your first missed period, we suggest taking a pregnancy test from the day you miss your first period.
Understanding Pregnancy Test Lines
Most pregnancy tests will indicate a positive result by showing two lines, a cross, a marker, or the word pregnant. If your test displays a positive result, then you have hCG present in your urine and you are pregnant.
A faint line or faint positive is still a positive. A pregnancy test only detects if hCG is present in your urine and reacts accordingly, displaying a positive result - regardless of how clear the result is.
DPO means Days Past Ovulation or Days Passed Ovulation. DPO is generally used by women who are trying to conceive and are watching the days that have passed since ovulating. Knowing the days past ovulation, DPO, can set a timeline for when to test for pregnancy and when to watch for symptoms of pregnancy.
DPO and Days before Period (28 day cycle)
|14 days before expected period
|13 days before expected period
|12 days before expected period
|11 days before expected period
|10 days before expected period
|9 days before expected period
|8 days before expected period
|7 days before expected period
|6 days before expected period
|5 days before expected period
|4 days before expected period
|3 days before expected period
|2 days before expected period
|1 day before expected period
|Expected period day
Earliest Tests to Buy
6 days before expected period or 8dpo
4 days before expected period or 10dpo
- Clearblue digital pregnancy test
- First Response Gold
- Accu-Clear Early Pregnancy Test
- e.p.t. Certainty
- Answer Quick and Simple Early Result Pregnancy Test
- Clearblue Easy
- Fact Plus One-Step Pregnancy Test
- CVS Digital Pregnancy Test
- Drugstore Pregnancy Tests
Majority of all early tests are available at local grocery or drug stores.
- Betz D, Fane K. Human Chorionic Gonadotropin. [Updated 2021 Aug 11; cited 2023 Mar 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan; https://www.ncbi.nlm.nih.gov/books/NBK532950/
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [updated 2022 Mar 24; cited 2023 Mar 3]; https://www.nhlbi.nih.gov/health/blood-tests
- Office on Women's Health [Internet]. Washington D.C.: U.S. Department of Health and Human Services; Knowing if you are pregnant; [updated 2021 Feb 22; cited 2023 Mar 3]; https://www.womenshealth.gov/pregnancy/you-get-pregnant/knowing-if-you-are-pregnant
- Medline Plus [Internet]. Washington D.C.: U.S. Department of Health and Human Services; Pregnancy Test; [updated 2021 Feb 22; cited 2023 Mar 3]; https://medlineplus.gov/ency/article/003432.htm