Medical calculators

This is a collection of popular medical calculators. Also check out MedCalc for other useful calculators.

#Body Mass Index (BMI)

Source: World Health Organization

BMI is a simple index of weight-for-height that is commonly used to classify underweight, overweight, and obesity in adults. It provides a useful population-level measure of overweight and obesity. However, BMI does not differentiate between body fat and muscle mass, so it's not a perfect measure.

Weight (kg)
Height (m)
 
Range Classification
< 18.5 Underweight
18.5-25 Normal
25-30 Overweight
30-35 Obese Class I (Moderate)
35-40 Obese Class II (Severe)
≥ 40 Obese Class III (Very severe or morbidly obese)

#Body Surface Area (Mosteller)

Source: Mosteller RD (1987)

The Mosteller formula is a commonly used method to calculate Body Surface Area, which is a measurement used in many medical tasks.

Height (cm)
Weight (kg)
 

#Corrected Calcium based on Albumin

Source: Payne RB, et al. (1973)

Calcium levels in the blood can be affected by albumin levels, as calcium binds to albumin. Correcting calcium based on albumin provides a more accurate representation of calcium levels in various clinical scenarios.

Measured Total Calcium (mg/dL)
Serum Albumin (g/dL)
Normal Albumin (g/dL)
 

#Corrected QT Interval

Source: Bazett HC (1920)

Source: Dmitrienke AA, et al. (2005)

Source: Fridericia LS (1920)

Source: Sagie A, et al. (1992, Framingham)

Source: Hodges MS, et al. (1983)

Source: Rautaharju PM, et al. (2014)

Calculates the corrected QT interval using various methods.

Correction Method
QT Interval (ms)
Heart Rate (bpm)
 
Category Males Females
Normal ≤ 440 ms ≤ 450 ms
Borderline 441-450 ms 451-460 ms
Prolonged > 450 ms > 460 ms
High Torsades de pointes risk > 500 ms > 500 ms

#Corrected Sodium for Hyperglycaemia

Source: Katz MA (1973)

Source: Hillier TA, et al. (1999)

Corrects serum sodium levels based on elevated blood glucose levels using various methods. Values are rounded to the nearest integer.

Correction Method
Measured Sodium (mmol/L)
Blood Glucose (mg/dL)
 

#Cycle Time to Heart Rate

Converts cycle time in milliseconds (ms) to heart rate in beats per minute (BPM) rounded to the nearest integer.

Cycle Time (ms)
 

#Heart Rate to Cycle Time

Converts heart rate in beats per minute (BPM) to cycle time in milliseconds (ms).

Heart Rate (BPM)
 

#LDL Calculation (Friedewald Equation)

Source: Friedewald WT, Levy RI and Fredrickson DS (1972)

Estimates LDL cholesterol using the Friedewald equation, which requires total cholesterol, HDL cholesterol, and triglycerides.

Total Cholesterol (mg/dL)
HDL Cholesterol (mg/dL)
Triglycerides (mg/dL)
 
LDL Level (mg/dL) Interpretation
< 100 Optimal
100-130 Near/Above Optimal
130-160 Borderline High
160-190 High
≥ 190 Very High

#MDRD GFR Equation

Source: Levey AS, et al. (1999)

The MDRD formula is a widely used equation to estimate the glomerular filtration rate based on serum creatinine, age, and race.

Serum Creatinine (µmol/L)
Age
Sex
Race
 

#Mean Arterial Pressure (MAP)

The MAP is an average blood pressure in an individual. It's used to give a general overview of blood flow and perfusion. A normal MAP is usually 70-110 mmHg.

Diastolic Blood Pressure (mmHg)
Systolic Blood Pressure (mmHg)
 

#MELD Score Calculation

Source: Kamath PS, et al. (2001)

Calculates the MELD score based on serum creatinine, serum bilirubin, and INR, used to assess the severity of chronic liver disease.

On Hemodialysis?
Serum Creatinine (mg/dL)
Serum Bilirubin (mg/dL)
INR (International Normalized Ratio)
 
MELD Score 3-Month Mortality Risk
< 9 1.9%
10-19 6.0%
20-29 19.6%
30-39 52.6%
≥ 40 71.3%