BUN Creatinine Ratio Calculator

BUN Creatinine Ratio Calculator for Nephrology. The repaired output supplies no diagnostic risk band. Values at 10.05, 20.05 or above 100 have the same neutral interpretation rather than falling through decimal gaps.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

The conventional ratio is BUN mg/dL divided by creatinine mg/dL. SI blood urea is multiplied by 2.8 and SI creatinine divided by 88.4 before division. Urea mass in mg/dL is not the same analyte convention as BUN.

When to use this calculator

Describing the relationship between two contemporaneous laboratory measurements, alongside rather than instead of clinical evaluation.

Inputs used

  • Blood urea (SI) / BUN (US) (mmol/L; US mg/dL)
  • Serum creatinine (umol/L; US mg/dL)

Clinical interpretation

The repaired output supplies no diagnostic risk band. Values at 10.05, 20.05 or above 100 have the same neutral interpretation rather than falling through decimal gaps.

Worked example

BUN 60 mg/dL and creatinine 1.2 mg/dL give 50. The matching SI values are approximately 21.43 mmol/L urea and 106.08 umol/L creatinine. A ratio 100.01 remains a valid numerical output without false normal reassurance.

Limitations and safety notes

The ratio alone does not distinguish prerenal from intrinsic AKI or establish gastrointestinal bleeding, hydration or fluid responsiveness. Protein metabolism, drugs, liver function, muscle mass and timing can affect its inputs.

Frequently asked questions

Does a high ratio prove dehydration?

No. Multiple processes change BUN and creatinine, and a ratio cannot select fluid treatment without the clinical context.

What does this result leave unresolved?

The ratio alone does not distinguish prerenal from intrinsic AKI or establish gastrointestinal bleeding, hydration or fluid responsiveness. Protein metabolism, drugs, liver function, muscle mass and timing can affect its inputs.

References

  • https://pubmed.ncbi.nlm.nih.gov/28545421/

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

Related reviewed calculators