National Forestry Inventory analytical tools found there was 8% more woodland across England, Scotland and Wales than 2010's estimate.
The latest estimate is 2,982,000 ha, against 2010's 2,757,000ha.
This represents 13% of Britain's land area.
The improved results are due to improved technology such as aerial photography, satellite imagery, and the inclusion of small woods in urban areas.
The Forestry Commission has undertaken surveys since 1924.