Medical Equations

 

 
Click a letter to jump to that section. Click on a link below to use a formula or criteria.
 
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A

A-a Gradient

a/A Ratio

AaPO2 Correction for FIO2

Absolute Eosinophil Count

Absolute Lymphocyte Count

Absolute Neutrophil Count

Absolute Phagocyte Count

Absolute Reticulocyte Count

Acute Heart Failure Prediction Based on NT-proBNP and Clinical Features

Adjusted Cerebrospinal Fluid White Blood Cell Count in the Presence of Red Blood Cells

Allowable Blood Loss

Aminoglycoside Clearance Estimate

Anion Gap Delta Delta Gradient Multicalc

Anion Gap Delta Delta Ratio Multicalc

Anion Gap in Hypoalbumin States

Anion Gap

Ascites Albumin Gradient

 

B

Basal Energy Expenditure (Harris-Benedict estimation)

Base Excess Determination

Bayesian Statistics I MultiCalc

Bayesian Statistics II MultiCalc

Benefit Increase / Number Needed to Treat Multicalc

Bicarbonate Deficit

Blood Ethanol Concentration Estimation

Blood pressure percentiles for boys 0 to 17 years old (revised 2017)

Blood Pressure Percentiles for Boys 2 to 17 years old (2004 standard)

Blood pressure percentiles for girls 0 to 17 years old (revised 2017)

Blood Pressure Percentiles for Girls 2 to 17 years old (2004 standard)

Body Mass Index (BMI Quetelet's index)

Body Mass Index (BMI) percentiles for boys (2 to 20 years)

Body Mass Index (BMI) percentiles for girls (2 to 20 years)

Body Surface Area (BSA, Du Bois Method)

Body Surface Area (BSA, Gehan and George Method)

Body Surface Area (BSA, Mosteller, square root method)

Body Surface Area Based Dosing

Burn Injury Fluid Resuscitation (Brooke estimate)

Burn Injury Fluid Resuscitation (Demling dextran estimate)

Burn Injury Fluid Resuscitation (Evans estimate)

Burn Injury Fluid Resuscitation (Modified Brooke crystalloid estimate)

Burn Injury Fluid Resuscitation (Slater estimate)

Burn Injury Fluid Resuscitation, Adult (Parkland crystalloid estimate)

 

C

Calcium Correction in Hypoalbuminemia (SI units)

Calcium Correction in Hypoalbuminemia

Calorie Requirements for Weight Maintenance and Weight Loss in Men (Patient information)

Calorie Requirements for Weight Maintenance and Weight Loss in Women (Patient information)

Carbon Dioxide Production

Cardiac Output MultiCalc

Cardiac Output Using Oxygen Saturation Data Only

Cardiac Output

CDC Height for Age Percentiles for Boys (2 to 20 years)

CDC Height for Age Percentiles for Girls (2 to 20 years)

CDC Stature for Age Graph for Girls (2 - 20 years)

CDC Weight for Age Percentiles for Boys (2-20 years)

CDC Weight for Age Percentiles for Girls (2-20 years)

CDC Weight for Height Percentiles for Boys (77-121 cm tall)

CDC Weight for Height Percentiles for Girls (77-121 cm tall)

CDC/NCHS Infant Growth Percentiles (<36 months)

CDC/NCHS Infant Head Circumference for Age Percentiles (<36 months)

CDC/NCHS Infant Length for Age Percentiles (<36 months)

CDC/NCHS Infant Weight for Age Percentiles (<36 months)

CDC/NCHS Infant Weight for Length Percentiles (<36 months)

Chi Square Analysis

Closing Capacity to Total Lung Volume Capacity

Closing Capacity

Closing Volume to Vital Capacity Ratio

Confidence Interval of a Binomial Proportion

Confidence Interval of a Difference Between Proportions

Confidence Interval of a Ratio of Proportions

Confidence Interval of a Ratio of Ratios

Confidence Interval of a Survey

COPE Statistic Adding Cost to Number Needed to Treat

Creatinine Clearance (measured)

Creatinine Clearance (measured, SI units)

Creatinine Clearance by Mass

Creatinine Clearance Estimate by Cockcroft-Gault Equation (SI units)

Creatinine Clearance Estimate by Cockcroft-Gault Equation with Ideal Body Weight

Creatinine Clearance Estimate by Cockcroft-Gault Equation

Creatinine Clearance Estimate by Jelliffe Formula

Creatinine Clearance Estimate by Sanaka Formula (for older subjects with low muscle mass)

Creatinine Kinetics MultiCalc

CSF IgG Index

CSF Protein Concentration Correction in Blood Contaminated CSF

 

D

Diffusing capacity for carbon monoxide (DLCO) corrected for anemia

Diffusing capacity for carbon monoxide (DLCO) correction of predicted value for anemia (SI units)

Digitalis Body Load

Dose Adjustment for Body Surface Area

Dose Driven IV-Drip Rate Calculator

Dynamic International Prognostic Scoring System-Plus (DIPSS-Plus) for Primary Myelofibrosis (PMF) in Adults and Adolescents

 

E

Endotracheal tube size for children (Age 1 to 8 years)

Energy Loss Index and the Severity of Asymptomatic Aortic Stenosis

England Fraser Index for Differentiating Beta-thalassemia Trait from Iron-deficiency

Epidural Formulation Compounding Calculator

Estimated 24 Hour Urine Protein Excretion in Pregnancy (from spot urine protein to creatinine ratio)

Estimated Blood Volume

Estimated Date of Delivery (EDD) Pregnancy Calculator

Estimated Delivery Date (Patient information)

 

F

False Negative Rate from Sensitivity and Prevalence

False Negative Ratio from Sensitivity and Prevalence

False Positive Rate from Specificity and Prevalence

False Positive Ratio from Specificity and Prevalence

Fat Free Mass, a Measure of Lean Body Weight

Fractional Excretion of Amylase (Amylase to creatinine clearance ratio)

Fractional Excretion of Magnesium (SI units)

Fractional Excretion of Magnesium

Fractional excretion of phosphate (FePO₄)

Fractional Excretion of Sodium (FENa)

Fractional Excretion of Sodium (FENa, SI units)

Fractional Excretion of Urate

Fractional Excretion of Urea (FEUrea)

Friedewald Equation for Low Density Lipoprotein (LDL-C)

Friedewald Equation for Low Density Lipoprotein (LDL-C, SI units)

Functional Residual Capacity

 

G

Gestational Age from Estimated Date of Delivery (EDD)

Glomerular Filtration Rate (GFR) Estimate by CKD-EPI Equation

Glomerular Filtration Rate (GFR) Estimate by Quadratic Equation

Glomerular Filtration Rate (GFR) Estimate by Schwartz Formula

Glomerular Filtration Rate (GFR) Estimate by the Abbreviated MDRD Study Equation (SI units)

Glomerular Filtration Rate (GFR) Estimate by the Abbreviated MDRD Study Equation

Glomerular Filtration Rate (GFR) Estimate by the IDMS-Traceable MDRD Study Equation

Glomerular Filtration Rate (GFR) Estimate by the MDRD Equation (SI units)

Glomerular Filtration Rate (GFR) Estimate by the MDRD Equation

Glomerular Filtration Rate (GFR) Estimate by Updated Schwartz Formula

Glomerular Filtration Rate (GFR) Estimate in African Americans by AASK Equation

Glycemic Assessment: A1C to Average Glucose Conversions

Gorlin Formula for Valve Area

Gravity Flow Rate Calculator

Green King Index for Differentiating Beta-thalassemia Trait from Iron-deficiency

 

H

Height Potential: A Child's Target Height Based on Midparental Height

Henderson-Hasselbach Equation

Hepatitis C Fibrosis Prediction Score

HOMA Formula: Homeostasis Model Assessment of Insulin Resistance

Housestaff Activity Index

Hyponatremia Correction Infusate Rate

 

I

Ideal body weight (method of Devine) and adjusted body weight for adults

Ideal Body Weight Percentage

Ideal Body Weight

In-Flight PaO2 Estimation (using PFT's)

In-Flight PaO2 Estimation

Injury Severity Score (ISS)

Inspiratory Capacity

International Normalized Ratio of Prothrombin Time (INR)

IV Drip Maintenance Rate Calculator

 

K

Kappa Measurement of Inter-observer Agreement MultiCalc

Kappa Measurement of Inter-observer Agreement: Bennett's Kappa

Kappa Measurement of Inter-observer Agreement: Cohen's Kappa

Kappa Measurement of Inter-observer Agreement: Scott's Kappa

Kt/V Dialysis Dose Barth Formula

Kt/V Dialysis Dose Basile Formula

Kt/V Dialysis Dose Daugirdas Formula

Kt/V Dialysis Dose Formulae MultiCalc

Kt/V Dialysis Dose Jindal Formula

Kt/V Dialysis Dose Kerr Formula

Kt/V Dialysis Dose Keshaviah Formula

Kt/V Dialysis Dose Lowrie Formula

 

L

Lean Body Weight (Female)

Lean Body Weight (Male)

Lean Body Weight Based on Creatinine Production

Likelihood Ratio MultiCalc

Likelihood Ratio of Negative from Raw Data

Likelihood Ratio of Positive from Raw Data

Lung Age Estimation for Smoking Cessation Counseling

Lung Volume Multicalc

 

M

Maintenance fluid calculation for children based on daily fluid requirements

Maintenance Fluid Calculation for Children Based on Hourly Fluid Requirements

Mantle Cell Lymphoma International Prognostic Index (MIPI)

Mean Arterial Pressure (MAP) in Adults and Children (conventional or SI units)

Mean Corpuscular Hemoglobin Concentration

Mean Corpuscular Hemoglobin

Mean Corpuscular Volume

Mean Vascular Pressure (systemic or pulmonary)

MELD Score for End-Stage Liver Disease (NOT appropriate for patients under the age of 12) (SI units)

MELD Score for End-Stage Liver Disease (NOT appropriate for patients under the age of 12)

MELDNa Score (2008) for End-Stage Liver Disease (NOT appropriate for patients under the age of 12) (SI units)

MELDNa Score (2008) for End-Stage Liver Disease (NOT appropriate for patients under the age of 12)

MELDNa Score (2016) (SI units)

MELDNa Score (2016)

Mortality risk in post-operative patients with cirrhosis (SI units)

Mortality risk in post-operative patients with cirrhosis

 

N

Nasal Cannula Oxygen Fractional Inspired O₂ (FiO₂) Estimate

Negative Predictive Value from Raw Data

Negative Predictive Value of a Test

NIH Chronic Prostatitis Symptom Index

Normal Range for Body Weight

Number Needed to Harm (NNH) from Odds Ratio (OR) and Patient Expected Event Rate (PEER)

Number Needed to Treat (NNT) from Odds Ratio (OR) and Patient Expected Event Rate (PEER)

 

O

Odds from Probability

Odds Ratio and Relative Risk

Osmolal Gap Calculator (SI units)

Osmolal Gap Calculator

Osmolality Estimator (serum)

Osmolar Clearance

Overall Accuracy of a Test from Raw Data

Overall Accuracy of a Test from Sensitivity, Specificity and Prevalence

Oxygen Consumption

Oxygen Content of Arterial Blood

Oxygen Content of Venous Blood

Oxygen Saturation Estimate from PO2

Oxygenation Index (OI)

 

P

paO2 / FIO2 Ratio (for MODS Calculation)

PaO2 Correction for FIO2

PASI Psoriasis Area and Severity Index

Peak Expiratory Flow Prediction in adults

Peak expiratory flow prediction in boys (5 to <18 years)

Peak expiratory flow prediction in females (18 to 85 years)

Peak expiratory flow prediction in girls (5 to <18 years)

Peak expiratory flow prediction in males (18 to 85 years)

Peak Expiratory Flow Variability in Asthma

PELD Score for End-Stage Liver Disease (patients less than 12 years old)

PFT Adjusted Predicted Values for Men MultiCalc

PFT Adjusted Predicted Values for Women MultiCalc

PFT Predicted Values for Boys MultiCalc

PFT Predicted Values for Girls MultiCalc

PFT Predicted Values for Men MultiCalc

PFT Predicted Values for Women MultiCalc

Phenytoin Free (Unbound) Drug Level (Adjusted for Hypoalbuminemia)

Phenytoin Total Drug Level (Adjusted for Hypoalbuminemia and Renal Function)

Pneumothorax Degree of Collapse

Positive Predictive Value from Raw Data

Positive Predictive Value of a Test

Post Test Odds from Pre Test Odds and Likelihood Ratio MultiCalc

Post Test Odds of a Negative from Raw Data

Post Test Odds of a Negative Result from Sensitivity Specificity and Prevalence

Post Test Odds of a Positive from Raw Data

Post Test Odds of a Positive Result from Sensitivity Specificity and Prevalence

Post Test Probability from Pre Test Probability, Sensitivity and Specificity

Post-Test Probability from Likelihood Ratios and Multiple Test Results

Post-Test Probability from Sensitivity and Specificity of Multiple Test Results

Pre Test Odds from Prevalence

Pre Test Odds from Raw Data

Predicted postoperative FEV1 following lung resection surgery (anatomic method)

Predicted postoperative FEV1 following lung resection surgery (perfusion method)

Pregnancy Gestation by LMP and Ultrasound Biometry

Pressure Adjusted Heart Rate (For MODS calculation)

Prevalence of a Finding or Disease from Test Data

Probability from Odds

Protein Bound Calcium

Protein Catabolic Rate (normalized PCR)

Protein Catabolic Rate

Pulmonary Vascular Resistance

Pulse Pressure Variation (percentage)

 

Q

QT Interval Correction (EKG)

QUICKI Formula for Insulin Resistance

 

R

Renal Failure Index

Residual Renal Function in Hemodialysis Patients (Kru)

Residual Volume to Total Lung Capacity Ratio

Respiratory Quotient

Reticulocyte Production Index

Right to Left Shunt Fraction Qs/Qt

Risk Increase / Number Needed to Harm Multicalc

Risk Reduction / Number Needed to Treat Multicalc

ROX Index (Respiratory rate--oxygenation)

 

S

Sensitivity of a Test

Serum Sodium Concentration Change Considering Infused and Excreted Cations

Sodium Change in Hyperproteinemia

Sodium Change in Hypertriglyceridemia

Sodium Concentration Correction for Hyperglycemia (Emmett 2013)(conventional or SI units)

Sodium Correction in Hyperglycemia (Hillier 1999)

Sodium Correction in Hyperglycemia (Katz 1973)

Sodium Deficit in Hyponatremia

Specificity of a Test

Stool Osmolal Gap

Survey Sample Size with Population Correction

Survey Sample Size

Systemic Vascular Resistance

Systolic Pressure Variation (percentage)

 

T

Time Averaged Concentration of Urea in Hemodialysis

TIPS Risk predictor / Survival predictor (Transjugular Intrahepatic Portosystemic Shunt)

Total Body Water (BIA formula)

Total Body Water Estimation Based on Weight Alone

Total Body Water in Men (Humes-Weyer formula)

Total Body Water in Men (Johansson formula)

Total Body Water in Men (Lee formula)

Total Body Water in Men (Watson formula)

Total Body Water in Women (Humes-Weyer formula)

Total Body Water in Women (Johansson formula)

Total Body Water in Women (Lee formula)

Total Body Water in Women (Watson formula)

Total Daily Energy Requirement Estimate

Total Lung Capacity

Transferrin Receptor-Ferritin Index for Diagnosis of Iron deficiency Anemia

Transferrin Saturation

Transtubular Potassium Gradient at CCD

True Negative Ratio from Specificity and Prevalence

True Positive Ratio from Sensitivity and Prevalence

 

U

Urea Reduction Percentage in Hemodialysis (PRU)

Urea Reduction Ratio in Hemodialysis (URR)

Urinary Protein Excretion Estimation

Urine anion gap

Urine osmolal gap (UOG) (SI units)

Urine osmolal gap (UOG)

 

V

Ventilation Index

Very Low Density Lipoprotein (VLDL)

Vital Capacity

Volume of Distribution of Urea

 

W

Waist to Hip Ratio

Water Deficit in Hypernatremia

Weight Based Divided Dose Calculator

Weight Based Dosage Calculator

Weight Loss Indices Following Bariatric Surgery in Adults

WHO Assessment of Malnutrition in Boys 0 to 2 Years Old

WHO Assessment of Malnutrition in Boys 2 to 5 years Old

WHO Assessment of Malnutrition in Girls 0 to 2 Years Old

WHO Assessment of Malnutrition in Girls 2 to 5 years Old

WHO Infant Head Circumference for age Percentiles (<24 months)

WHO Infant Length for Age Percentiles (<24 months)

WHO Infant Weight for Age Percentiles (<24 months)

WHO Infant Weight for Length Percentiles (<24 months)

Winters' Formula for Expected PCO2

 

Z

Z Score to Percentile Estimation