Nephrology Calculators
Renal function tools — eGFR (CKD-EPI), creatinine clearance, FENa, BUN/creatinine ratio, and free water deficit.
This category currently includes 7 tools, including FENa Calculator, BUN/Cr Ratio, and Free Water Deficit.
These resources are built for clinicians, trainees, and medically informed patients who need fast bedside calculations. Use the results as decision support and pair them with full clinical context and local guidelines.
All Nephrology Tools (7)
FENa Calculator
Calculate the Fractional Excretion of Sodium (FENa) to differentiate pre-renal azotemia (FENa <1%) from intrinsic renal disease such as ATN (FENa >2%) in acute kidney injury.
BUN/Cr Ratio
Calculate the BUN/Creatinine ratio to distinguish pre-renal from intrinsic acute kidney injury. Normal ratio 10–20. Ratio >20 suggests pre-renal azotemia; <10 suggests intrinsic renal disease.
Free Water Deficit
Calculate free water deficit for hypernatremia using TBW × (serum Na/140 - 1), with practical 24-hour sodium correction targets and fluid-planning guidance.
Urine Anion Gap
Calculate the urine anion gap to differentiate GI from renal causes of non-anion gap metabolic acidosis. Negative UAG suggests GI bicarbonate loss; positive UAG suggests renal tubular acidosis.
24h Creatinine Clearance
Calculate measured creatinine clearance from a 24-hour urine collection. More accurate than estimated GFR in certain populations.
FEUrea Calculator
Calculate FEUrea to help distinguish pre-renal azotemia from intrinsic AKI, especially when diuretics make FENa unreliable.
Osmolar Gap
Calculate osmolar gap to screen for unmeasured osmoles such as toxic alcohols, ethanol, mannitol, or propylene glycol.