Miscarriage Risk Calculator by Week and Age
Enter your current pregnancy week, additional days and maternal age, then calculate your miscarriage risk estimate. The result uses the calculator's fixed gestational-age reference curve and shows age-related population context alongside it.
Reviewed for editorial and calculation accuracy: 7 October 2026.
This page was reviewed for calculation logic, source consistency, medical-safety wording and clarity. It is educational content and is not a substitute for diagnosis, ultrasound interpretation or advice from a qualified healthcare professional.
Calculate Your Chance of Miscarriage
Your estimated result
Estimated miscarriage risk
Estimated chance of not miscarrying
This is population-level educational context, not a personal prediction. A calculator cannot confirm pregnancy viability or diagnose miscarriage.
What Is the Baseline Miscarriage Risk by Week?
The table below uses the same fixed reference curve as the calculator. Values are shown at exactly 0 additional days for selected gestational weeks .
| Gestational age | Reference miscarriage risk | Chance of not miscarrying |
|---|---|---|
| Week 4 | 25% | 75% |
| Week 5 | 19% | 81% |
| Week 6 | 13.5% | 86.5% |
| Week 7 | 8.7% | 91.3% |
| Week 8 | 4.8% | 95.2% |
| Week 9 | 3.2% | 96.8% |
| Week 10 | 2.3% | 97.7% |
| Week 11 | 1.8% | 98.2% |
| Week 12 | 1.4% | 98.6% |
| Week 13 | 1.1% | 98.9% |
| Week 14 | 0.8% | 99.2% |
| Week 16 | 0.4% | 99.6% |
| Week 18 | 0.2% | 99.8% |
| Week 20 | <0.1% | >99.9% |
These values are calculator reference points, not personalised probabilities. The result may not reflect ultrasound findings, bleeding, pain, fetal heart rate, previous pregnancy history, IVF treatment or other medical factors.
What Does Your Miscarriage Risk Estimate Mean?
The percentage shown above corresponds to the gestational age you selected. Pregnancy dating matters when interpreting the result.
Why Do Miscarriage Risk Calculators Show Different Results?
Different calculators may use different populations, study designs, pregnancy stages or ultrasound criteria. Some estimates apply to all clinically recognised pregnancies, while others apply only after a particular ultrasound finding has been documented.
How Does Maternal Age Affect Miscarriage Risk Estimates?
Maternal age is required so the result can show relevant age-related population context alongside the week-and-day estimate. The calculator deliberately keeps the age context separate instead of multiplying two overlapping risk estimates together.
The age figures shown by the calculator are broad context only and should not be read as a personalised forecast.
How Does Ultrasound Dating Shift Your Risk Estimate?
Ultrasound dating can change the gestational age used to interpret a risk estimate. In early pregnancy, gestational-sac measurements or crown-rump length may provide more specific dating information than calendar estimates.
What Does This Miscarriage Calculator Not Include?
The main estimate does not incorporate bleeding, pain, fetal heart rate, previous miscarriage, IVF treatment, pregnancy location, laboratory trends, medical conditions or ultrasound viability findings.
How Is the Miscarriage Risk Calculated?
The main result comes from the fixed day-by-day gestational-age reference curve coded into this tool. The calculator is deterministic: the same week and day always return the same reference value. Generative AI does not create or alter the percentage.
Maternal age is deliberately shown separately because combining age and gestational-age figures with a simple arithmetic formula could imply a level of personalised validation that this calculator does not have.
Important calculation notes
The calculator uses one reference value for each selectable week-and-day point. It does not extrapolate beyond the available range.
When the reference curve reaches zero, the page displays less than 0.1% instead of implying that miscarriage becomes impossible.
Common Questions About Miscarriage Risk
Does miscarriage risk usually decrease each week?
In this calculator's reference curve, the estimated percentage generally decreases as gestational age advances. Individual assessment can differ because clinical and ultrasound information are not included.
Does seeing a heartbeat change miscarriage risk?
A documented fetal heartbeat provides clinical information that a general week-based estimate does not capture. A heartbeat-specific calculator or clinical interpretation of the ultrasound is more appropriate in that situation.
How accurate is a miscarriage risk calculator?
A calculator can provide population-level context, but it cannot determine whether an individual pregnancy is viable or predict its outcome.
When Should You Seek Medical Help?
A miscarriage calculator cannot assess symptoms. Seek prompt medical advice if you are pregnant and have symptoms that concern you. Urgent assessment is particularly important for:
- Heavy bleeding, rapidly soaking pads, or passing large clots or tissue.
- Severe or one-sided abdominal or pelvic pain, shoulder-tip pain, fainting, marked dizziness or weakness.
- Fever, chills or feeling acutely unwell, especially with pain or bleeding.
Evidence and Reference Notes
American College of Obstetricians and Gynecologists (ACOG). Early Pregnancy Loss.
Magnus MC, et al. Role of maternal age and pregnancy history in risk of miscarriage. BMJ. 2019;364:l869.
These sources provide clinical and population context. They should not be interpreted as validating every individual percentage in the calculator's fixed day-by-day curve.