The range of viral load is so wide that results are often given as results from a logarithmic (log) scale.

This is an easier way to deal with very large and very small numbers at the same time. Less than 50 copies/mL for most people on treatment is 1.7 logs. In very early infection, a viral load of 10 million copies is 7.0 logs.

Log value is a measurement used to describe HIV and expresses the viral load values as a power of ten (written log10). The scale is used because large changes can only be captured on graphs or diagrams by using a log scale. This turns large numbers of copies/mL into ‘manageable’ figures.

Table: HIV RNA viral load log value–number conversion

Log10 copies/mL
0.1 1
0.2 2
0.3 2
0.4 3
0.5 3
0.6 4
0.7 5
0.8 6
0.9 8
1.0 10
Log10 copies/mL
1.1 13
1.2 16
1.3 20
1.4 25
1.5 32
1.6 40
1.7 50
1.8 63
1.9 79
2.0 100
Log10 copies/mL
2.1 126
2.2 158
2.3 200
2.4 251
2.5 316
2.6 398
2.7 501
2.8 632
2.9 794
3.0 1,000
Log10 copies/mL
3.1 1,259
3.2 1,585
3.3 1,995
3.4 2,512
3.5 3,162
3.6 3,981
3.7 5,012
3.8 6,310
3.9 7,943
4.0 10,000
Log10 copies/mL
4.1 12,589
4.2 15,849
4.3 19,953
4.4 25,119
4.5 31,623
4.6 39,811
4.7 50,119
4.8 63,096
4.9 79,433
5.0 100,000
Log10 copies/mL
5.1 125,893
5.2 158,489
5.3 199,526
5.4 251,189
5.5 316,228
5.6 398,107
5.7 501,187
5.8 630,957
5.9 794,328
6.0 1,000,000

Last updated: 29 March 2010.