MediCalc (Medical Calculator)

MediCalc [medical calculator] contains over 70 of the most commonly used medical equations and scoring tools.
It has a very simple UI with formulas broken down by specialty and systems.

Equations:
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A-a O2 Gradient
Absolute Neutrophil Count (ANC)
Absolute Reticulocyte Count (Reticulocyte Index)
Age
Anion Gap
Basal Energy Expenditure
Bayesian Sensitivty, Specificity, Probabilities
Bicarbonate Deficit
BMI and Body Surface Area (BSA)
BMR and RMR
Calcium Correction for Hypoalbuminemia
Corrected QT Interval (QTc)
Creatinine Clearance (Cockcroft-Gault Equation)
CSF WBC Correction for RBCs
Endotracheal Tube (ETT) Size for Pediatrics
Fractional Excretion of Sodium (FENa)
Fractional Excretion of Urea (FEUrea)
Free Water Deficit in Hypernatremia
Ideal Body Weight
LDL Calculated
Maintenance Fluids Calculations
MDRD GFR Equation
Mean Arterial Pressure (MAP)
Oxygenation Index
Parkland Formula for Burns
Pediatric Ins and Outs (per kg and per hour)
Phenytoin/Dilantin Correction for Albumin or Renal Failure
Pregnancy Due Dates Calculator
Serum Osmolality/Osmolarity
Sodium Correction for Hyperglycemia
Sodium Correction Rate in Hyponatremia
Sodium Deficit in Hyponatremia
Stool Osmolar/Osmotic Gap
Transtubular Potassium Gradient (TTKG)
Winters' Formula for Metabolic Acidosis Compensation

Scores
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ABCD2 Score for TIA
APACHE II Score for ICU Mortality
APGAR Score
Blood Alcohol Concentration (BAC)
CHADS2 Score for Atrial Fibrillation Stroke Risk
Child-Pugh Score for Cirrhosis Mortality
CURB-65 Severity Score for Community-Acquired Pneumonia
EuroSCORE - Additive
EuroSCORE - Logistic
Framingham Cardiac Risk Score
Glasgow Coma Scale/Score
Glasgow-Blatchford Bleeding Score (GBS)
Hunt and Hess Classification of Subarachnoid Hemorrhage (SAH)
Intracerebral Hemorrhage (ICH) Score
Maddrey's Discriminant Function for Alcoholic Hepatitis
MELD Score (Model For End-Stage Liver Disease) (12 and older)
Modified Centor Score for Strep Pharyngitis
Ottawa and Pittsburgh Knee Rules
Ottawa Ankle Rules
Parkland Formula for Burns
PELD Score (Pediatric End-Stage Liver Disease) (younger than 12)
PERC Rule for Pulmonary Embolism
PSI/PORT Score: Pneumonia Severity Index for Adult CAP
Ranson's Criteria for Pancreatitis Mortality
San Francisco Syncope Rule to Predict Serious Outcomes
TIMI Risk Score for STEMI
TIMI Risk Score for UA/NSTEMI
Well's Criteria for DVT
Well's Criteria for Pulmonary Embolism / PE