MIC Calculator | Minimum Inhibitory Concentration Tool Online

MIC Calculation Parameters

Antimicrobial Agent *

Select the antimicrobial agent being tested

Inoculum Concentration (CFU/mL) *

CFU/mL

Standard is 5×10⁵ CFU/mL

Incubation Time *

hours

Typically 18-24 hours

Antimicrobial Concentration Range (µg/mL)

Min: 0.5 µg/mL

Max: 64 µg/mL

Adjust the concentration range for testing

Dilution Factor *

Two-fold (2×) √2-fold Custom

Number of Dilutions *

Growth Threshold (%) *

Bacterial Strain

Growth Inhibition Curve

Visual representation of bacterial growth inhibition at different antimicrobial concentrations

MIC Result

Minimum Inhibitory Concentration

16.0 µg/mL

Susceptible

Interpretation

Based on CLSI guidelines, the isolate is susceptible to this antimicrobial agent at the calculated MIC.

Breakpoint:

≤8 µg/mL

Resistance:

≥32 µg/mL

Dilution Series

#	Concentration (µg/mL)	Growth (%)	Inhibition	MIC Point

Additional Calculations

MIC₅₀ Estimate:

8.0 µg/mL

MIC₉₀ Estimate:

32.0 µg/mL

Therapeutic Index:

12.5

Resistance Risk:

Low

Calculation History

Amoxicillin - Staphylococcus aureus

16.0 µg/mL

Just now

Understanding MIC: A Guide to Minimum Inhibitory Concentration Testing

The Minimum Inhibitory Concentration (MIC) is the lowest concentration of an antimicrobial agent that inhibits visible growth of a microorganism. This essential microbiology measurement helps determine the susceptibility of bacteria to antibiotics and plays a crucial role in clinical decision-making for antibiotic therapy.

How to Use This MIC Calculator

Our real-time MIC calculator simplifies the process of determining antimicrobial susceptibility:

Select the antimicrobial agent from the dropdown list (e.g., amoxicillin, ciprofloxacin)
Set the inoculum concentration (typically 5×10⁵ CFU/mL for standard testing)
Adjust the concentration range using the sliders to match your dilution series
Choose the dilution factor (two-fold dilutions are standard for MIC testing)
Specify the number of dilutions in your test series
Set the growth threshold - the percentage of growth considered as inhibition
Click "Calculate MIC" to get instant results with interpretation

Interpreting MIC Results

MIC values are interpreted using established breakpoints from organizations like CLSI (Clinical and Laboratory Standards Institute) and EUCAST (European Committee on Antimicrobial Susceptibility Testing):

Susceptible (S): The isolate is inhibited by the usually achievable concentrations of the antimicrobial agent
Intermediate (I): The isolate is inhibited by concentrations that are possibly achievable with specific dosing adjustments
Resistant (R): The isolate is not inhibited by the usually achievable concentrations of the agent

Applications of MIC Testing

MIC determination is crucial in several contexts:

Clinical microbiology: Guiding appropriate antibiotic therapy for bacterial infections
Antimicrobial stewardship: Promoting optimal antibiotic use to combat resistance
Research and development: Evaluating new antimicrobial compounds
Veterinary medicine: Determining effective treatments for animal infections
Food safety: Testing for antimicrobial residues and resistance patterns

Limitations and Considerations

While MIC calculators provide valuable estimates, laboratory testing remains essential for clinical decisions. Factors such as bacterial inoculum size, incubation conditions, medium composition, and method used can all influence MIC results. This tool is designed for educational and preliminary assessment purposes.

For accurate clinical decisions, always consult with a microbiology laboratory and consider additional factors such as pharmacokinetics/pharmacodynamics (PK/PD), patient-specific factors, and local resistance patterns.