The Hit40UK, which airs on commercial radio, will no longer use CD sales to collate its weekly chart.
From this weekend, the countdown, which broadcasts across 130 stations, will use digital sales only.
Owner Global Radio said digital download sales now account for 96% of all chart data.
"Downloads have now become the driving force for record sales, as the statistics clearly show,” said programme director Paul Jackson.
"It makes complete sense to reflect the changes in how people are listening to music.”
The chart, which attracts 1.9million listeners every Sunday, is seen as an alternative to the official UK singles run down.