If a translation of a given charter has been published, this should become clear from the entry for the charter in the 'Electronic Sawyer'.
Only a relatively small proportion of royal diplomas, in Latin, have been translated into modern English. The largest selection appears in English Historical Documents c. 500-1042, ed. Dorothy Whitelock. Several diplomas in the 'Electronic Sawyer' have been provided with translations specially made for the project by Dr David Pelteret.
All texts in the vernacular, published in the series comprising Harmer's Select English Historical Documents of the Ninth and Tenth Centuries (1914), Whitelock's Anglo-Saxon Wills (1930), and Robertson's Anglo-Saxon Charters (1939), were accompanied by translations into modern English. These books might be found in academic libraries, and all three are available in modern paperback reprints.
The project intends to continue to collect translations of charters, and to make them readily accessible online.