Phred Quality Score Converter
This online program converts between Phred quality scores and error probabilities.
The Phred quality score of a nucleotide is an number representing the estimated probability that that nucleotide is incorrect. The FASTQ format encodes phred scores as ASCII characters.
| Phred Quality Score | Probability of incorrect base call | Base call accuracy |
|---|---|---|
| 10 | 0.1 (1 in 10) | 90% |
| 20 | 0.01 (1 in 100) | 99% |
| 30 | 0.001 (1 in 1000) | 99.9% |
| 40 | 0.0001 (1 in 10,000) | 99.99% |