Try this script - it will list the number of rows and the space used by data rows (and the total space used) for all tables in your database:

SELECT
t.NAME AS TableName,
i.name AS indexName,
SUM(p.rows) AS RowCounts,
SUM(a.total_pages) AS TotalPages,
SUM(a.used_pages) AS UsedPages,
SUM(a.data_pages) AS DataPages,
(SUM(a.total_pages) * 8) / 1024 AS TotalSpaceMB,
(SUM(a.used_pages) * 8) / 1024 AS UsedSpaceMB,
(SUM(a.data_pages) * 8) / 1024 AS DataSpaceMB
FROM
sys.tables t
INNER JOIN
sys.indexes i ON t.OBJECT_ID = i.object_id
INNER JOIN
sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id
INNER JOIN
sys.allocation_units a ON p.partition_id = a.container_id
WHERE
t.NAME NOT LIKE 'dt%' AND
i.OBJECT_ID > 255 AND
i.index_id <= 1
GROUP BY
t.NAME, i.object_id, i.index_id, i.name
ORDER BY
OBJECT_NAME(i.object_id)

Use sp_spacedUsed

Exec sp_spaceused N'YourTableName'

Or if you want to execute the sp_spaceused for each table in your database then you can use this SQL:

set nocount on
create table #spaceused (
name nvarchar(120),
rows char(11),
reserved varchar(18),
data varchar(18),
index_size varchar(18),
unused varchar(18)
)


declare Tables cursor for
select name
from sysobjects where type='U'
order by name asc


OPEN Tables
DECLARE @table varchar(128)


FETCH NEXT FROM Tables INTO @table


WHILE @@FETCH_STATUS = 0
BEGIN
insert into #spaceused exec sp_spaceused @table
FETCH NEXT FROM Tables INTO @table
END


CLOSE Tables
DEALLOCATE Tables


select * from #spaceused
drop table #spaceused


exec sp_spaceused

The above SQL is from here

Rossisdead's comment answered this question the best for me, I wish it wasn't buried in a comment. This will be useful for people like me not trying to script the solution (the OP did not ask for a code snippet)

If you're using Management Studio you can also right click on the database and go to Reports -> Disk Usage by Table for the same results

Thanks to @marc_s for the answer. I needed to know data vs index space so I went ahead and expanded on the query to include that.

SELECT TableName
, SUM(DataRowCounts) AS DataRowCounts
, SUM(DataTotalSpaceGB) AS DataTotalSpaceGB
, SUM(DataSpaceUsedGB) AS DataSpaceUsedGB
, SUM(DataUnusedSpaceGB) AS DataUnusedSpaceGB
, SUM(IndexRowCounts) AS IndexRowCounts
, SUM(IndexTotalSpaceGB) AS IndexTotalSpaceGB
, SUM(IndexSpaceUsedGB) AS IndexSpaceUsedGB
, SUM(IndexUnusedSpaceGB) AS IndexUnusedSpaceGB
, SUM(DataTotalSpaceGB) + SUM(IndexTotalSpaceGB) AS TotalSpaceGB
FROM
(
SELECT t.NAME AS TableName
, i.type_desc AS IndexType
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS DataTotalSpaceGB
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN CAST(ROUND(((SUM(a.used_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2))  ELSE 0 END AS DataSpaceUsedGB
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN CAST(ROUND(((SUM(a.total_pages) - SUM(a.used_pages)) * 8) / 1024.00, 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS DataUnusedSpaceGB
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN SUM(p.Rows) ELSE 0 END AS DataRowCounts
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS IndexTotalSpaceGB
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN CAST(ROUND(((SUM(a.used_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2))  ELSE 0 END AS IndexSpaceUsedGB
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN CAST(ROUND(((SUM(a.total_pages) - SUM(a.used_pages)) * 8) / 1024.00, 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS IndexUnusedSpaceGB
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN SUM(p.Rows) ELSE 0 END AS IndexRowCounts
FROM sys.tables t
INNER JOIN sys.indexes i ON t.OBJECT_ID = i.object_id
INNER JOIN sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id
INNER JOIN sys.allocation_units a ON p.partition_id = a.container_id
LEFT JOIN sys.schemas s ON t.schema_id = s.schema_id
WHERE t.NAME NOT LIKE 'dt%'
AND t.is_ms_shipped = 0
AND i.OBJECT_ID > 255
AND s.Name = 'dbo' --update this filter
AND t.Name = 'MyTable'
GROUP BY t.Name
, i.type_desc
) x
GROUP BY TableName
ORDER BY TotalSpaceGB DESC