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14 Nephrology Calculators – Kidney Function, Electrolytes & Urine

Nephrology calculators cover kidney-function and dialysis estimates, serum electrolyte and water arithmetic, acid-base measures, urine ratios, output, and fractional excretion. Their inputs and intended uses differ even when the same analyte appears.

Keep specimen identity, collection duration, dialysis-session timing, and model-specific assumptions aligned with the selected page.

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Find a Nephrology calculator

Search the calculators in this category by name, short name, or the task description. The full task-group listing remains below.

Enter a term to narrow this category; all calculators remain available in the task groups below.

Which tool fits this task?

Compare the purpose, inputs, and returned measure before opening a calculator. These distinctions describe tool scope; they do not make a diagnosis or choose treatment.

Kidney-function estimates

These kidney-function estimates differ in biomarker inputs, indexing, weight use, and model purpose.

Adult eGFR Calculator

Use when
Estimate indexed GFR with the selected adult CKD-EPI creatinine, cystatin-C, or combined model.
Inputs
Supported serum biomarkers, age, and sex inputs.
Returns
An indexed eGFR estimate in mL/min/1.73 m².
Distinction
eGFR is indexed and model-specific; it is not Cockcroft–Gault clearance or dialysis adequacy.

Cockcroft–Gault Creatinine Clearance Calculator

Use when
Calculate the historical adult Cockcroft–Gault creatinine-clearance estimate when that metric is required.
Inputs
Serum creatinine, age, sex branch, and an explicitly supplied weight basis.
Returns
Estimated creatinine clearance in mL/min.
Distinction
The page does not automatically select a weight or produce a medication dose.

Fractional excretion calculations

Both are paired urine/serum ratios, but they use different analytes and neither provides a universal AKI-cause cutoff.

Fractional Excretion of Sodium (FENa) Calculator

Use when
Calculate fractional sodium excretion from paired urine and serum analytes.
Inputs
Paired urine/serum sodium and independently normalized creatinine.
Returns
FENa as a percentage.
Distinction
It returns arithmetic without a universal cutoff, AKI-cause label, or treatment output.

Fractional Excretion of Urea (FEUrea) Calculator

Use when
Calculate paired urine/serum FEUrea or FEUN when the page's urea and creatinine inputs are available.
Inputs
Paired urine/serum BUN or whole urea plus independently normalized creatinine.
Returns
FEUrea/FEUN as a percentage.
Distinction
It is a distinct urea-based calculation and is not an automatic replacement for FENa.

Choose a calculator by task

Use the task groups below to find the calculator whose formula, intended population, required measurements, and purpose match the task.

Kidney-function and dialysis estimates

Choose between adult CKD-EPI eGFR, historical Cockcroft–Gault creatinine clearance, and protocol-dependent hemodialysis adequacy arithmetic.

Adult eGFR CalculatorEstimate adult race-free indexed glomerular filtration rate (eGFR) with 2021 CKD-EPI creatinine, 2012 cystatin C, or 2021 combined equations.CrClCockcroft–Gault Creatinine Clearance CalculatorEstimate adult Cockcroft–Gault creatinine clearance in mL/min from an explicit weight basis, without automatic weight selection or a dosing recommendation.spKt/V & URRAdult Single-Pool Kt/V (Daugirdas II) & URR CalculatorCalculate adult Daugirdas II single-pool Kt/V and URR for one completed intermittent hemodialysis treatment using paired sampling and actual delivered time; no adequacy classification or prescription.

Serum electrolytes, osmolality, and water

Use measured serum inputs and the specified units for hyperglycemia-adjusted sodium, calculated osmolality, or free-water-deficit arithmetic.

Adjusted Na⁺Hyperglycemia-Adjusted Sodium Calculator (Katz & Hillier)Compare Katz 1.6 and Hillier overall 2.4 hyperglycemia-adjusted sodium estimates from measured sodium and paired glucose in mg/dL or mmol/L, without selecting a primary model.Calculated Serum Osmolality, Tonicity & Osmolal Gap CalculatorCalculate serum osmolality and effective osmolality (tonicity), with optional measured osmolality, osmolal gap, and separate ethanol assumptions; no toxic-alcohol or HHS diagnosis.Free Water Deficit Calculator (Explicit TBW Coefficient)Estimate a static positive free water deficit for hypernatremia when current sodium is >145 mmol/L or mEq/L, using an explicitly selected lower target, kg or lb weight, and an explicit TBW coefficient, with estimated TBW and results in L and mL—not an infusion volume or treatment output.

Acid-base arithmetic

Select the albumin-adjusted serum anion gap, urine anion gap, or bicarbonate-deficit estimate according to the required measurements and assumptions.

Adjusted AGAlbumin-Adjusted Anion Gap Calculator (Figge 2.5)Calculate a signed sodium-only Figge 2.5 albumin-adjusted anion gap from same-specimen or paired chemistry and albumin in g/dL or g/L, with no universal interval, diagnosis, delta ratio, or treatment output.Urine Anion Gap Calculator (Na + K − Cl)Calculate the one-decimal signed urine anion gap from sodium, potassium, and chloride in the same urine specimen using mmol/L or mEq/L, without treating UAG as direct urine ammonium or a universal positive/negative diagnosis.Estimated Bicarbonate Deficit Calculator (Explicit Distribution Factor)Estimate a static positive bicarbonate deficit in mEq from submitted bicarbonate, an externally selected higher target, kg or lb weight, and an explicit distribution factor; not blood-gas base deficit, a sodium bicarbonate dose, product volume, or treatment output.

Urine and renal-handling measures

Match urine protein, urine output, BUN/creatinine, FENa, or FEUrea inputs to the stated collection and paired-sample requirements.

Spot Urine Protein-to-Creatinine Ratio Calculator (UPCR / PCR)Calculate a same-specimen spot urine total protein-to-creatinine ratio in mg/mg, mg/g, and mg/mmol; not ACR, 24-hour protein, or a diagnosis.Measured Urine Output Rate Calculator (mL/hr & mL/kg/hr)Calculate measured urine output for one completed collection interval as average mL/hr and average mL/kg/hr using protocol-selected weight, without AKI diagnosis, stage, or treatment output.BUN/Cr RatioBUN-to-Creatinine Ratio CalculatorCalculate a same-specimen or clinically paired conventional BUN-to-creatinine ratio after exact normalization of BUN mg/dL or urea mmol/L and creatinine mg/dL or µmol/L, without diagnostic or treatment output.Fractional Excretion of Sodium (FENa) CalculatorCalculate fractional excretion of sodium from paired urine and serum sodium plus independently normalized urine and serum creatinine in mg/dL or µmol/L, returning a percentage without a universal cutoff, AKI-cause classification, or treatment output.Fractional Excretion of Urea (FEUrea) CalculatorCalculate paired urine and serum FEUrea (FEUN) after independent exact normalization of BUN mg/dL or whole urea mmol/L and urine/serum creatinine in mg/dL or µmol/L, with no AKI-cause or treatment output.

Kidney-function estimates are not interchangeable

  • Keep paired serum and urine measurements, collection duration, units, and timing aligned before calculating fractional excretion or urine measures.
  • For Kt/V, use the stated pre/post hemodialysis sampling, postdialysis weight, and completed-session timing rather than mixing unrelated values.
  • Non-steady-state biomarkers, indexing, weight basis, and model boundaries can change what a kidney estimate represents; do not silently substitute one output for another.

Important limits

  • A calculated kidney-function or urine result does not by itself diagnose acute kidney injury or chronic kidney disease.
  • Changing biomarkers, non-steady-state creatinine, collection error, and nonrenal determinants can limit these estimates.
  • These pages do not generate medication doses, dialysis prescriptions, referral instructions, or treatment decisions.

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