Pregnancy-Test Calculator

Professional pregnancy-testing tool: supports both urine & blood HCG testing, intelligently calculates the best testing date, accurately interprets results, provides stick-usage guidance and false-positive/negative analysis, helps TTC moms choose the right moment and avoid mis-judgement caused by too-early testing.

Calculate Best Test Date View Features

Precise Pregnancy-Test Date Calculation

Choose your test method and conception info; the system will automatically give the best test date and professional guidance

Affects HCG production timing
Default 28; 21-45 is normal
Days from ovulation to period
Please select the exact ovulation or intercourse date
Affects prediction accuracy
Please select the first bleeding day
Number of bleeding days
Date of embryo transfer or insemination
Affects HCG production timing
Common range: 10-50 mIU/mL
Usually 6-12 days
Normal range 24-72 h

Urine vs Blood HCG Detection

Learn the pros & cons of each method and pick the one that suits you

Urine HCG (Home Test)
Detection time:
10-14 days after ovulation
Accuracy:
75-99%
  • Easy, can be done at home
  • Private, instant result
  • Low cost, available everywhere
  • Relatively late detection
  • Technique & timing sensitive
  • Risk of false pos/neg
For: routine home self-testing
Blood HCG
Detection time:
6-8 days after ovulation
Accuracy:
95-99%
  • Earliest detection, 6-8 dpo
  • Highest accuracy, up to 99%
  • Exact HCG number
  • Can track doubling trend
  • Requires clinic visit
  • Higher cost
For: urgent confirmation or special cases
Pro Tip

Use a home stick first; if positive confirm with blood. Blood gives the most accurate number and helps monitor early pregnancy.

Pregnancy-Test Science

What is HCG hormone?

HCG (human chorionic gonadotropin) is a glycoprotein hormone secreted by placental trophoblast cells and is the most important biochemical marker of early pregnancy.

After the embryo implants, the placenta begins to form and secretes HCG, whose level increases exponentially in early pregnancy, doubling every 48-72 h.

Key facts
  • Production starts 6-8 days after implantation
  • Doubles every 48-72 h
  • Peaks at weeks 8-11
  • Disappears 2-3 weeks post-delivery

Scientific Principle of Pregnancy Tests

Understand how different methods work and choose the one that suits you

Urine-test Principle

Detects HCG hormone in urine

Principle: Immunochromatography detecting HCG β-subunit

Sensitivity: 10-50 mIU/mL

Detection: 10-14 days after ovulation

Blood-test Principle

Quantifies exact HCG number in blood

Principle: Chemiluminescent immunoassay giving exact concentration

Sensitivity: 1-5 mIU/mL

Detection: 6-8 days after ovulation

HCG Change Pattern

Know the normal growth curve

Doubling: 48-72 h

Peak: weeks 8-11

Range: huge individual variation

Accuracy Factors

Learn what may influence result

Timing: too early → false neg

Technique: wrong steps → invalid

Drugs: certain meds → false pos

Professional Advice

Choose the right timing and avoid mis-judgement and anxiety caused by too-early testing.

Best Testing Timing

Optimal test time

Test after your period is 7 days late; HCG is then high enough and accuracy reaches 99%.

Early-test strategy

12-14 days after ovulation: early testing possible but lower accuracy

  • If negative, re-test in 2-3 days
  • Use high-sensitivity stick (10-25 mIU/mL)
  • First-morning urine is best
Detection Accuracy
7 dpo: <50%
10 dpo: 60-70%
12 dpo: 80-90%
Period late: >99%

Correct Usage Guide for Home Test Sticks

Before use
  • Choose right time: 7 days after missed period or 12-14 dpo
  • Check expiry: ensure stick is not expired
  • First-morning urine best: highest concentration
  • Avoid excess water: dilute urine affects result
Operation steps
  • Read leaflet: brands differ slightly
  • Correct sampling: place stick in urine stream or cup as instructed
  • Wait time: lay flat 5-10 min (per leaflet)
  • Read promptly: result invalid after 10 min
Important reminder

Sensitivity differs among brands; choose well-known ones. If unclear, re-test in 2 days or switch brand.

Common Questions Quick Answers

Q: How soon can a home test detect pregnancy?

A: Usually 10-14 days after ovulation, but accuracy rises with time. After a missed period accuracy reaches 99%.

Q: One dark and one faint line—pregnant?

A: Weak positive means low HCG. Re-test in 2-3 days; if the line darkens pregnancy is very likely.

Q: What causes false positives?

A: Recent birth/miscarriage, certain drugs (HCG-containing), some diseases, expired stick, chemical pregnancy, etc.

Q: Period late but test negative—why?

A: Maybe tested too early, wrong operation, dilute urine, or period delayed by stress, weight change, hormone imbalance, etc.

Q: How much more accurate is blood?

A: Blood is 99% accurate, detects 1-5 mIU/mL, can test 2-4 days earlier, gives exact numbers and doubling trend.

Q: When should I go to hospital for confirmation?

A: As soon as home test is positive, go for blood confirmation. Especially if pain, bleeding, ectopic risk, or under ART.

Why Choose PreMami Pregnancy-Test Calculator?

Multi-Method Support

Supports both urine & blood HCG testing, gives detailed timing advice and accuracy analysis

Smart HCG Prediction

Medical-data-based model predicts HCG trend and shows visual charts

Personalised Timing

Automatically generates personalised test-date advice based on your conception mode and cycle features

Professional Interpretation

Provides detailed result interpretation, false-positive/negative analysis and next-step advice

Frequently Asked Questions

Usually 10-14 days after ovulation, but accuracy rises with time. Testing after a missed period gives the highest accuracy (99%). High-sensitivity sticks (10-25 mIU/mL) may detect earlier, yet too-early testing can yield false negatives.

A weak positive (faint line) means HCG is detected but still at a low level, likely in very early pregnancy. Re-test with first-morning urine in 2-3 days; if the test line darkens, pregnancy is very probable.

Common causes: recent birth/miscarriage with residual HCG; certain medicines (e.g., HCG-containing fertility drugs); some tumours; expired or improperly stored sticks; chemical pregnancy (brief HCG rise without ongoing pregnancy). If suspected, re-test or have a blood test.

Blood HCG accuracy reaches 99%, clearly higher than urine (75-99%). Blood can detect lower HCG (1-5 mIU/mL vs 10-50 mIU/mL), so it detects pregnancy 2-4 days earlier and gives exact numbers useful for monitoring doubling and ruling out abnormal pregnancy.

May be testing too early, operating incorrectly, urine too dilute, or period delayed by other factors (stress, weight change, hormone imbalance, etc.). Re-test in 2-3 days or choose a more sensitive method.

As soon as the home stick is positive, go for a blood test. Especially if: result is unclear or keeps changing; you have pain or bleeding; ectopic risk factors exist; or you are under assisted-reproduction treatment. Doctors can combine blood HCG and ultrasound for accurate diagnosis and guidance.

Use first-morning urine for highest concentration; check expiry and package integrity; follow leaflet strictly regarding dip time and reading window; avoid drinking too much water before testing; read result within 5-10 min (brand-dependent); if unclear, re-test in 2 days or switch brand.

Individual variation is huge. Reference ranges: 3-4 weeks: 5-426 mIU/mL; 4-5 weeks: 19-7,340 mIU/mL; 5-6 weeks: 1,080-56,500 mIU/mL. More important than a single number is the doubling trend: in normal pregnancy HCG doubles every 48-72 h.