Enter the Total Antibiotic Resistance and Total Antibiotic Use into the calculator to determine the Antibiotic Resistance Index. This calculator can also evaluate any of the variables given the others are known.

Antibiotic Resistance Index Formula

The following formula is used to calculate the Antibiotic Resistance Index (ARI).

ARI = (TAR / TAU) * 100


  • ARI is the Antibiotic Resistance Index (%)
  • TAR is the Total Antibiotic Resistance (number of resistant strains)
  • TAU is the Total Antibiotic Use (number of antibiotic doses used)

To calculate the Antibiotic Resistance Index, divide the Total Antibiotic Resistance by the Total Antibiotic Use. Multiply the result by 100 to convert it into a percentage. This will give you the Antibiotic Resistance Index, which indicates the level of antibiotic resistance in a population.

What is an Antibiotic Resistance Index?

An Antibiotic Resistance Index is a measure used to quantify the level of resistance a bacterial strain has to a particular antibiotic or group of antibiotics. It is calculated based on the minimum inhibitory concentration (MIC) of the antibiotic required to inhibit the growth of the bacteria. A higher index indicates a higher level of resistance, suggesting that larger doses of the antibiotic are needed to effectively treat an infection caused by the bacteria. This index is crucial in understanding the spread and impact of antibiotic resistance, aiding in the development of effective treatment strategies.