Renal & Nephrology Calculators

Estimates GFR using race-free CKD-EPI 2021 creatinine equation. Defines CKD staging.

Estimates creatinine clearance for weight-based drug dosing (not for CKD staging).

Distinguishes pre-renal from intrinsic renal AKI using urine and serum sodium and creatinine.

Better than FENa for distinguishing pre-renal from intrinsic AKI in patients on diuretics.

Stages acute kidney injury by creatinine rise from baseline or urine output criteria.

Adjusts serum calcium for albumin level to obtain true calcium status.

Calculates anion gap to evaluate causes of metabolic acidosis (MUDPILES vs NAGMA).

Modification of Diet in Renal Disease (MDRD) 4-variable equation for estimating GFR. Largely superseded by CKD-EPI but still widely reported by laboratories.

Calculates the estimated free water deficit in patients with hypernatraemia to guide fluid replacement therapy.

Calculates the corrected (true) serum sodium in hyperglycaemic states (DKA, HHS). Hyperglycaemia causes osmotic dilution of sodium — the corrected value guides fluid resuscitation.

Calculates estimated serum osmolarity from sodium, glucose, and urea. Compare with measured osmolality to detect an osmol gap (suggesting toxic alcohols or other unmeasured osmoles).

Calculates the urine anion gap (UAG = urine Na⁺ + K⁺ − Cl⁻) to differentiate renal from non-renal causes of normal anion gap (hyperchloraemic) metabolic acidosis.

Estimates aldosterone activity by assessing potassium secretion in the collecting duct. Used to differentiate causes of hyperkalaemia (renal vs extra-renal) and hypokalaemia.

Calculates the bicarbonate deficit to guide sodium bicarbonate replacement in severe metabolic acidosis.

The delta ratio (delta anion gap / delta bicarbonate) identifies mixed acid-base disorders in the presence of a high anion gap metabolic acidosis. It reveals whether a concurrent metabolic alkalosis or normal anion gap acidosis is also present.

The ratio of blood urea nitrogen (urea) to creatinine helps differentiate pre-renal from intrinsic renal causes of acute kidney injury, and can identify upper GI bleeding.

Original AKI staging system (Risk, Injury, Failure, Loss, End-stage) based on creatinine rise, GFR reduction, and urine output. Predecessor to KDIGO AKI staging.

Calculates the volume of hypertonic saline (3% NaCl) or normal saline needed to correct hyponatraemia at a safe rate, preventing osmotic demyelination syndrome (ODS).

Calculates the calcium-phosphate product to assess risk of metastatic calcification in chronic kidney disease (CKD), particularly vascular and soft tissue calcification.

Calculates maintenance fluid requirements using the Holliday-Segar method: 100 mL/kg for first 10 kg, 50 mL/kg for next 10 kg, 20 mL/kg thereafter. Also provides hourly rate (4-2-1 rule).

Predicts the likelihood of an uncomplicated ureteral stone on CT-KUB in patients presenting with flank pain. Score 0–13.

Calculates expected respiratory compensation (PaCO₂) in metabolic acidosis using Winter's formula. Helps identify concurrent respiratory acid-base disorders.

Spot urine protein:creatinine ratio estimates 24-hour urinary protein excretion without timed urine collection.

Classifies CKD stage by eGFR and albuminuria category (G1-G5, A1-A3) per KDIGO 2012 guidelines.

Estimates total body potassium deficit in hypokalaemia. Used to guide IV/oral potassium replacement.

Classifies hyponatraemia severity and guides safe correction rate. Maximum correction: 10 mmol/L in 24 hours (6–8 mmol/L in high-risk patients) to prevent osmotic demyelination syndrome (ODS).

Identifies absolute and relative indications for initiating RRT (dialysis) in acute kidney injury. Uses AEIOU mnemonic.

Calculates blood pH from bicarbonate and partial pressure of CO2 (pCO2). Fundamental tool for acid-base interpretation. Complements the stepwise ABG approach.

Acute Kidney Injury Network (AKIN) staging for AKI. Modification of RIFLE criteria using serum creatinine and urine output over 48 hours.

Predicts risk of acute kidney injury requiring RRT in rhabdomyolysis. Score ≥6 = high risk, warrants aggressive IV fluid therapy.

Predicts 50% eGFR decline or end-stage renal disease in IgA nephropathy at 5 and 20 years. Combines clinical and histological (Oxford MEST-C) criteria.

KDIGO (Kidney Disease Improving Global Outcomes) prognosis grid for CKD using GFR and albuminuria categories. Identifies low, moderate, high, and very high risk of CKD progression.

Measures adequacy of haemodialysis. Kt/V represents clearance (K) × time (t) / volume of distribution (V). Target: single-pool Kt/V ≥1.4 (KDOQI) or URR ≥65%.

Estimates GFR during acute kidney injury when creatinine is non-steady-state. More accurate than standard eGFR equations during AKI where creatinine is rising or falling.

Stages chronic kidney disease (CKD) by GFR category (G1-G5) and albuminuria category (A1-A3) per KDIGO 2012 guidelines.

Stages acute kidney injury (AKI) severity using KDIGO 2012 criteria based on creatinine rise and urine output.

Calculates single-pool Kt/V using the Daugirdas formula to assess adequacy of haemodialysis. Target Kt/V >=1.4 per session (thrice weekly).

Corrects total serum calcium for hypoalbuminaemia. Ionised calcium is the physiologically active fraction.

Stratifies hyperkalaemia severity and guides emergency treatment based on potassium level and ECG changes.

Differentiates pre-renal AKI from intrinsic renal AKI. FENa <1% suggests pre-renal cause; >2% suggests intrinsic renal disease.

Estimates 24-hour urinary protein excretion from spot urine protein and creatinine. Used to quantify proteinuria in CKD, nephrotic syndrome, and pre-eclampsia.

Classifies renal transplant rejection using Banff criteria from biopsy findings. Guides pulse steroids, antibody-mediated therapy, and transplant team management.