Bilirubin Nomogram Calculator

Calculator

Measurement type

Curves are intended for serum values.

Bilirubin value

Units

Converted using 1 mg/dL = 17.104 µmol/L.

Age at sample (hours)

Or compute from dates below.

Birth date/time (optional)

Sample date/time (optional)

Gestational age at birth (weeks)

Birth weight (kg)

Neurotoxicity risk factors (check any)

Isoimmune hemolysis

G6PD deficiency

Asphyxia

Significant lethargy

Temperature instability

Sepsis

Acidosis

Albumin < 3.0 g/dL (if measured)

Used only for legacy treatment group selection.

Reset

Reminder: Treatment thresholds shown here are “legacy curves” used in older references and tools. Always verify against your current guideline.

Example data table

Illustrative examples only. Do not use these example rows for patient care.

Age (hours)	Bilirubin (mg/dL)	Gestational age (weeks)	Risk factors present	Bhutani zone result
24	7.0	39.0	No	Low-intermediate (40th–<75th)
48	13.0	38.0	Yes	High-intermediate (75th–<95th)
72	18.0	36.5	Yes	High risk (≥95th percentile)

Formula used

Unit conversion: mg/dL = µmol/L ÷ 17.104, and µmol/L = mg/dL × 17.104.
Interpolation: Curves are stored as discrete points. For an age between points: y = y1 + (t − t1) × (y2 − y1) ÷ (t2 − t1).
Risk zone: Compare bilirubin to 40th, 75th, and 95th percentile lines at that age to classify the zone.
Legacy thresholds: Select a risk group from gestational age and risk factors, then compare bilirubin to phototherapy and exchange curves.

How to use this calculator

Enter the measured bilirubin value and select the correct unit.
Enter age in hours, or supply birth and sample times.
Add gestational age and birth weight to check applicability.
Tick any neurotoxicity risk factors if present.
Press Calculate to see results above the form.
Use CSV or PDF buttons to export the latest result.

FAQs

1) What does the Bhutani zone mean?

The zone estimates risk of later significant jaundice based on age and bilirubin. It is not a diagnosis. Clinical follow-up depends on the baby’s overall condition, feeding, and local protocols.

2) Why is age in hours important?

Bilirubin normally rises and then peaks over time. A value that is expected at 72 hours may be concerning at 18 hours. Hour-specific curves account for this change.

3) Can I use transcutaneous values (TcB)?

You can enter TcB, but the classic nomogram is based on serum values. Devices may under- or over-estimate. Confirm with serum testing when clinically indicated, especially near thresholds.

4) Are the treatment thresholds current?

No. The included treatment curves are legacy thresholds commonly used in older tools. Current guidelines may differ. Always verify decisions with your latest institutional or national guidance.

5) What if the baby is under 12 hours old?

The Bhutani risk-zone boundaries are defined from about 12 hours onward. For earlier values, interpret carefully and follow clinical guidance, especially if jaundice appears very early.

6) Does gestational age change risk?

Yes. Younger gestational age increases vulnerability. Many protocols adjust follow-up or treatment thresholds based on gestation and risk factors. This tool flags limited validity for very preterm infants.

7) Why do you ask about risk factors?

Risk factors can lower the acceptable bilirubin threshold in some guidance. In this calculator they are used only to select the legacy risk group for treatment comparisons, not to change Bhutani percentiles.

8) Can this replace medical judgement?

No. Calculations can support communication and documentation, but clinical evaluation is essential. Always consider feeding, weight loss, hemolysis, infection, and overall appearance before making care decisions.