Forests area change estimates are crucial for estimating forest-related emissions and removals in the REDD+ context. This two-lesson course emphasize that the use of rigorous activity data, produced according to good practices, is key to meeting monitoring, verification and reporting (MRV) requirements of REDD+ programmes and standards. Following good practices in area estimation based on the stratification derived from a forest change map, the first lesson introduces the sample-based area estimation (SBAE) workflow. The second lesson advances the learner using a stepwise approach to conducting a SBAE. In doing so accuracy is assessed following good practices and confidence intervals (a common technical requirement in REDD+ Programmes and Standards) are calculated.