±Free
Z-score calculator
Standardize a value relative to a known mean and positive standard deviation.
Enter the observation, reference mean and standard deviation. The tool returns z = (value − mean) / standard deviation; a negative result places the value below the supplied mean.
How to use
- Enter your text, values, or image.
- Adjust the options and run the tool.
- Copy or download your result.
Worked example
Example input
Value: 130 Mean: 100 Standard deviation: 15
Example result
2
Limitations and details
The standard deviation must be positive; the score alone does not imply a normal distribution or a probability.
Inputs and options
- Value
- Number
- Mean
- Number
- Standard deviation
- Number
Frequently asked questions
Is this tool free and private?
Yes. All 300 tools are free in this phase. Processing happens in your browser; your input and files are not sent to our servers.