Evidence-Based Clinical Calculators

Standardized diagnostic formulas verified against published clinical benchmark cases with dual SI and conventional units.

22 Golden-Standard Equations

Categories:Acid-Base & ElectrolytesRespiratory & Critical CareRenal & FluidsHepatology & GastroenterologyCardiology & VascularNeurology AssessmentObstetrics & Pediatrics

Acid-Base & Electrolytes2 Benchmark Cases

Serum Anion Gap & Albumin-Corrected Anion Gap

Calculates serum anion gap with Figge albumin correction to unmask occult high-anion-gap metabolic acidosis in hypoalbuminemia.

AG = Na⁺ - (Cl⁻ + HCO₃⁻)

4 inputs • Instant previewLaunch

Acid-Base & Electrolytes2 Benchmark Cases

Delta Gap & Delta-Delta Ratio (ΔAG / ΔHCO₃⁻)

Evaluates complex mixed acid-base disorders in high anion gap metabolic acidosis (HAGMA) by comparing the change in anion gap to the change in bicarbonate.

ΔAG = Anion Gap - 12

4 inputs • Instant previewLaunch

Acid-Base & Electrolytes2 Benchmark Cases

Winter's Formula & Respiratory Compensation Suite

Calculates expected respiratory compensation (PaCO₂) in primary metabolic acidosis to diagnose concurrent primary respiratory acidosis or alkalosis.

Expected PaCO₂ (mmHg) = (1.5 × HCO₃⁻) + 8 ± 2

2 inputs • Instant previewLaunch

Respiratory & Critical Care2 Benchmark Cases

Alveolar-Arterial Oxygen Gradient (A-a Gradient)

Measures the integrity of alveolar-capillary gas exchange to differentiate extrapulmonary hypoventilation from intrinsic pulmonary parenchymal or vascular disease.

P_A O₂ = (P_atm - 47) × FiO₂ - (PaCO₂ / 0.8)

5 inputs • Instant previewLaunch

Acid-Base & Electrolytes2 Benchmark Cases

Corrected Calcium for Hypoalbuminemia (Payne Formula)

Estimates true physiological ionized calcium fraction when total calcium is skewed by hypoalbuminemia or hyperalbuminemia.

In mg/dL: Corrected Ca = Total Ca + 0.8 × (4.0 - Albumin [g/dL])

2 inputs • Instant previewLaunch

Acid-Base & Electrolytes2 Benchmark Cases

Corrected Sodium for Hyperglycemia (Katz & Hillier Formulas)

Estimates true intravascular sodium concentration by correcting for the osmotic shift of water from the intracellular to extracellular fluid in marked hyperglycemia (DKA, HHS).

Hillier (Consensus): Corrected Na = Measured Na + 0.024 × (Glucose [mg/dL] - 100)

3 inputs • Instant previewLaunch

Renal & Fluids2 Benchmark Cases

Fractional Excretion of Sodium (FENa) & Urea (FEUrea)

Distinguishes prerenal azotemia from intrinsic acute tubular necrosis (ATN) in acute kidney injury. FEUrea provides reliable interpretation when loop diuretics invalidate FENa.

FENa (%) = (U_Na × S_Cr) / (S_Na × U_Cr) × 100

7 inputs • Instant previewLaunch

Acid-Base & Electrolytes2 Benchmark Cases

Serum Osmolality & Osmolar Gap

Calculates serum osmolality and the osmolar gap to screen for occult toxic alcohol ingestions (methanol, ethylene glycol, isopropanol, propylene glycol).

In Conventional (mg/dL): Calculated Osm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (Ethanol / 4.6)

5 inputs • Instant previewLaunch

Renal & Fluids2 Benchmark Cases

eGFR CKD-EPI 2021 (Race-Free) & Cockcroft-Gault CrCl

Computes standardized estimated glomerular filtration rate using the official 2021 race-free CKD-EPI creatinine equation, alongside Cockcroft-Gault clearance for pharmacy dosing.

CKD-EPI 2021: eGFR = 142 × min(SCr/κ, 1)^α × max(SCr/κ, 1)^-1.200 × 0.9938^Age × (1.012 if female)

4 inputs • Instant previewLaunch

Hepatology & Gastroenterology2 Benchmark Cases

Non-Invasive Liver Fibrosis Suite (FIB-4, APRI, De Ritis Ratio)

Comprehensive non-invasive liver risk stratification combining FIB-4 index, APRI score, and De Ritis (AST/ALT) ratio for non-alcoholic fatty liver disease (MASLD/MASH) and viral hepatitis.

De Ritis = AST / ALT

5 inputs • Instant previewLaunch

Cardiology & Vascular2 Benchmark Cases

Wells Criteria for DVT & Pulmonary Embolism (with Age-Adjusted D-Dimer)

Clinical pre-test probability scoring for Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), integrated with Age-Adjusted D-Dimer guidance (ADJUST-PE) to safely avoid unnecessary CT imaging.

Wells DVT: Score -2 to 8 (Low ≤ 0, Moderate 1-2, High ≥ 3)

9 inputs • Instant previewLaunch

Hepatology & Gastroenterology2 Benchmark Cases

MELD-Na (2016 UNOS) & Child-Pugh Cirrhosis Staging

End-stage liver disease mortality prognostication and liver transplant allocation using the official 2016 OPTN/UNOS MELD-Na equation and classic Child-Pugh classification.

MELD(i) = 9.57 × ln(Cr) + 3.78 × ln(Bili) + 11.2 × ln(INR) + 6.43

8 inputs • Instant previewLaunch

Respiratory & Critical Care2 Benchmark Cases

CURB-65 Pneumonia Severity Score

Stratifies community-acquired pneumonia mortality risk to guide outpatient vs inpatient vs ICU disposition. Each letter is 1 point.

CURB-65 (each = 1 point): Confusion (new AMT ≤8) · Urea >7 mmol/L (BUN >19 mg/dL) · RR ≥30 · BP (SBP <90 or DBP ≤60) · Age ≥65

6 inputs • Instant previewLaunch

Neurology Assessment2 Benchmark Cases

Glasgow Coma Scale (GCS)

Standardized objective assessment of impaired consciousness from three responses — eye, verbal, motor. Score 3 (deep coma) to 15 (fully alert).

GCS = Eye (1–4) + Verbal (1–5) + Motor (1–6), total 3–15

3 inputs • Instant previewLaunch

Cardiology & Vascular2 Benchmark Cases

CHA₂DS₂-VASc Stroke Risk in Atrial Fibrillation

Estimates annual ischemic-stroke risk in non-valvular atrial fibrillation to guide oral anticoagulation decisions.

C Congestive HF +1 · H Hypertension +1 · A₂ Age ≥75 +2 · D Diabetes +1 · S₂ Stroke/TIA/thromboembolism +2 · V Vascular disease +1 · A Age 65–74 +1 · Sc Sex category (female) +1

8 inputs • Instant previewLaunch

Cardiology & Vascular2 Benchmark Cases

HAS-BLED Major Bleeding Risk Score

Estimates 1-year risk of major bleeding on anticoagulation in atrial fibrillation. A score ≥3 flags high risk and modifiable factors — it should prompt review, not automatically stop anticoagulation.

H Hypertension (uncontrolled, SBP >160) +1 · A Abnormal renal/liver function (1 each) +2 · S Stroke history +1 · B Bleeding history/predisposition +1 · L Labile INR (TTR <60%) +1 · E Elderly >65 +1 · D Drugs (antiplatelet/NSAID) or alcohol (1 each) +2

9 inputs • Instant previewLaunch

Respiratory & Critical Care2 Benchmark Cases

PERC Rule — Pulmonary Embolism Rule-Out

Eight clinical criteria that, when ALL negative in a patient already assessed as low pre-test probability, rule out pulmonary embolism without any D-dimer or imaging.

PERC (all 8 must be NEGATIVE to rule out PE):

8 inputs • Instant previewLaunch

Obstetrics & Pediatrics2 Benchmark Cases

Apgar Newborn Score (1 & 5 minutes)

Rapid standardized assessment of newborn viability and response to resuscitation, scored at 1 and 5 minutes across five signs (0–2 each).

Apgar = Appearance (colour) + Pulse (HR) + Grimace (reflex irritability) + Activity (muscle tone) + Respiration — each 0–2, total 0–10

5 inputs • Instant previewLaunch

Obstetrics & Pediatrics2 Benchmark Cases

Modified Bishop Score (Cervical Favourability)

Predicts likelihood of successful induction of labour and vaginal delivery from five cervical/pelvic examination findings (0–2 or 0–3 each).

Modified Bishop = Dilation (0–3) + Effacement (0–3) + Station (0–3) + Consistency (0–2) + Position (0–2), total 0–13

5 inputs • Instant previewLaunch

Obstetrics & Pediatrics2 Benchmark Cases

Pediatric Maintenance IV Fluids (Holliday–Segar 4-2-1)

Calculates hourly and 24-hour maintenance fluid requirement from weight using the 4-2-1 rule, plus deficit and standard isotonic replacement fluid choice.

Holliday–Segar (4-2-1): first 10 kg → 4 mL/kg/h · next 10 kg → +2 mL/kg/h · each kg above 20 → +1 mL/kg/h

2 inputs • Instant previewLaunch

Hepatology & Gastroenterology2 Benchmark Cases

Ranson's Criteria — Acute Pancreatitis Severity

Predicts severity and mortality in acute (non-gallstone) pancreatitis. Phase-1 criteria are scored at admission; Phase-2 criteria at 48 hours. Each is 1 point.

At admission: Age >55 · WBC >16 ×10⁹/L · Glucose >200 mg/dL (>11 mmol/L) · LDH >350 IU/L · AST >250 IU/L

11 inputs • Instant previewLaunch

Respiratory & Critical Care2 Benchmark Cases

qSOFA — Quick Sepsis-Related Organ Failure Screen

A three-point bedside prompt to identify patients with suspected infection who are at risk of poor outcomes and warrant escalation (SOFA, lactate, escalation of care).

qSOFA (each = 1 point): Respiratory rate ≥22 · Altered mentation (GCS <15) · Systolic BP ≤100 mmHg

3 inputs • Instant previewLaunch