Gingival Bleeding Index Calculator
Ainamo-Bay Gingival Bleeding Index — dichotomous bleeding on probing score with percentage calculation, gingivitis severity classification, and EMR-ready periodontal documentation.
NMClinically reviewed byDr. Nikhil Mahajan, PT, MPT · Jan 15, 2026GBI Classification — Ainamo-Bay Reference
| GBI % | Gingivitis severity | Clinical implication | Action |
|---|---|---|---|
| 0% | Healthy | No gingival inflammation detected | Routine maintenance |
| 1–9% | Acceptable | Minimal bleeding — periodontal maintenance target | Positive reinforcement, continue recall |
| 10–25% | Mild gingivitis | Localised to generalised mild inflammation | OHI reinforcement, professional cleaning, 4–6 month recall |
| 26–50% | Moderate | Generalised gingivitis — significant plaque control deficit | Full mouth debridement, intensive OHI, 3-month recall |
| >50% | Severe gingivitis | Severe generalised gingivitis — consider systemic factors | Urgent periodontal assessment, medical history review, 3-month recall |
What Is the Gingival Bleeding Index?
The Gingival Bleeding Index (GBI) was developed by Ainamo and Bay in 1975 as a simple, reproducible, and dichotomous measure of gingival inflammation through bleeding on probing. Unlike the Gingival Index of Löe and Silness (which uses a 0–3 ordinal scale), the GBI records only the presence or absence of bleeding after gentle probing of the gingival sulcus — making it faster to administer and free from subjective inter-examiner variability in colour assessment.
Clinical Significance of Bleeding on Probing
Bleeding on probing (BoP) is the most sensitive clinical indicator of active gingival inflammation. Its absence has a high negative predictive value for periodontal disease progression — a site that does not bleed on probing is unlikely to be actively losing attachment. The GBI is therefore used not only to assess treatment need but to monitor treatment response in periodontal maintenance patients.