SQL Server - Space Being Used

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For Datafiles
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use [databaseName]
DBCC showfilestats

An "Extent" in SQL Server is 64 K. So the amount of space in megabytes allocated to Data file can be calculated by using the following formula:

Space Allocated for Data = TotalExtents * 64.0 / 1024.0

And the amount of space in megabytes used by Data can be calculated using the following formula:

Space Used for Data = UsedExtents * 64.0 / 1024.0

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For Logfiles
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DBCC sqlperf(logspace)

Transaction Log Space Used = Log Size (MB) * Log Space Used (%).