Calculate a Bishop score from cervical dilation, effacement, station, consistency, and position to gauge cervical favorability for a labor induction.
Bishop Score Formula
The Bishop score is a sum, not a product. You give each of five cervical exam findings a point value and add them together:
Bishop Score = Dilation + Effacement + Station + Consistency + Position
The clinical modifier variant adds historical adjustments to the five findings. This is one version of a modified score; naming and cutoffs vary. The adjusted total can fall outside 0 to 13, so the calculator shows the unadjusted score separately.
Modified Score = Bishop Score + Parity + Preeclampsia - Postdates - Nulliparity - PROM
The simplified score uses only the three findings that best predict a vaginal birth:
Simplified Score = Dilation + Effacement + Station
Variables:
- Dilation is how open the cervix is in centimeters, scored 0 (closed), 1 (1 to 2 cm), 2 (3 to 4 cm), or 3 (5 cm or more)
- Effacement is how thin the cervix is as a percentage, scored 0 (0 to 30 percent), 1 (40 to 50 percent), 2 (60 to 70 percent), or 3 (80 percent or more)
- Station is how low the baby sits relative to the ischial spines, scored 0 (-3), 1 (-2), 2 (-1 or 0), or 3 (+1 or +2)
- Consistency is how soft the cervix feels, scored 0 (firm), 1 (medium), or 2 (soft)
- Position is where the cervix points, scored 0 (posterior), 1 (mid), or 2 (anterior)
The standard score ranges from 0 to 13. The clinical modifier variant adds one point for preeclampsia and each prior vaginal delivery, and subtracts one each for postdates pregnancy, nulliparity (no prior birth), and premature or prolonged rupture of membranes. These historical modifiers are documented in this obstetric manual. No universal clinical cutoff is applied to the adjusted total. Simplified mode uses dilation, effacement, and station on a 0 to 9 scale.
Bishop Score Chart and What the Result Means
Use this chart to turn each exam finding into points. It is the same table the calculator applies behind the scenes.
| Finding | 0 points | 1 point | 2 points | 3 points |
|---|---|---|---|---|
| Dilation (cm) | Closed | 1 to 2 | 3 to 4 | 5 or more |
| Effacement (%) | 0 to 30 | 40 to 50 | 60 to 70 | 80 or more |
| Station | -3 | -2 | -1 or 0 | +1 or +2 |
| Consistency | Firm | Medium | Soft | – |
| Position | Posterior | Mid | Anterior | – |
The next table summarizes common descriptions of the standard score. There is no exact conversion to a simplified score. In the Laughon study, a simplified threshold above 5 had similar predictive performance to a standard threshold above 8 in the study population; that does not make the two scores interchangeable.
| Standard score | Simplified comparison | Cervix | What it usually means |
|---|---|---|---|
| 0 to 6 | No exact conversion | Unfavorable (unripe) | Lower cervical readiness; discuss induction options with your care team. |
| 7 | No exact conversion | Borderline | Between common descriptive bands; clinical context matters. |
| 8 to 13 | No exact conversion | Favorable (ripe) | Greater cervical readiness; this does not guarantee vaginal birth. |
Example Problems
Example 1: Standard score.
A cervix is 3 to 4 cm dilated (2), 60 to 70 percent effaced (2), at station -1 (2), soft (2), and anterior (2). The total is 2 + 2 + 2 + 2 + 2 = 10 out of 13, generally described as more favorable. It does not guarantee an induction outcome.
Example 2: Simplified score.
For dilation of 5 cm (3), effacement of 80 percent (3), and station 0 (2), the simplified total is 3 + 3 + 2 = 8 out of 9. This exceeds the study threshold of 5; it is not an exact conversion of the standard score in Example 1.
Frequently Asked Questions
What is a good Bishop score for induction?
A standard score of 8 or more generally indicates greater cervical readiness. A score of 6 or less indicates lower readiness, while 7 lies between these descriptive bands. NICE guidance uses 6 or less versus more than 6 when discussing induction methods. Your care team selects the method using the complete clinical situation, not this score alone.
What is the difference between the Bishop score and the modified Bishop score?
This calculator preserves a historical clinical modifier variant: the same five findings plus the listed positive and negative adjustments. It accepts the whole number of prior vaginal deliveries instead of capping that contribution at three. Modified Bishop score can also refer to other scoring systems; confirm which system your clinician uses. The adjusted total is shown as points, not as a value out of 13.
What is the simplified Bishop score?
The simplified score uses dilation, effacement, and station, with a range of 0 to 9. The 2011 Laughon study compared a simplified score above 5 with a standard score above 8 and reported positive predictive values of 87.7% and 87.0%, respectively. Those are study-population results, not an individual probability or a recommendation about treatment.
