How to use the phred quality score calculator
Convert a Phred quality score into the base call error probability and accuracy. Enter phred quality score in the field above; the error probability, base call accuracy are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “Phred score”, “base call accuracy”, “quality score to error rate”, “calculate phred quality score”, “find error probability”.
Formula
Variables
- Q — Phred quality score
Worked example
With phred quality score = 30, the calculator gives error probability ≈ 0.1 %; base call accuracy ≈ 99.9 %.
Frequently asked questions
What is the phred quality score calculator used for?
Convert a Phred quality score into the base call error probability and accuracy. It helps with questions such as “Phred score”, “base call accuracy”, “quality score to error rate”.
What is the formula for the phred quality score calculation?
Error probability (%) = 100 × 10^(-Q / 10). Base call accuracy (%) = 100-[Error probability]. Here Q is phred quality score.
What inputs do I need for the phred quality score calculator?
You need phred quality score. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the phred quality score calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the phred quality score result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.