First, keep in mind that neither Dispensationalism nor Reformed/Calvinism fit neatly into tight boxes. There's a great deal of theological/philosophical diversity/variation in both realms. Clarity is important, so I'll strive to keep it as simple as possible.

The best approach to answering the question might be to mention what core beliefs they share in common, before proceeding to their CORE difference(s). (PS. I've spent nearly 55 years exploring these realms. When I reference "Dispensationalism," I historically trace the doctrine distinctions to John Nelson Darby (JND) and his Classical Pauline view(s). The most definitive resources here are the extensive works of the late Roy A. Huebner.)

COMMON: Both Reformed/Calvinism and Classical Pauline Dispensationalism share a belief in the Sovereignty of God and the epistemological foundation of the Inerrant Word of God--the 66 Books of the Bible. Both believe that Election and Salvation are based on God's Grace and Mercy, apart from ANY form of merit.

DIFFERENCE: Reformed/Calvinism follows traditional Christendom in the use of God's covenants made with earthly Israel to superimpose a forced continuity to the 66 books of Scripture. By contrast, Dispensationalism held this obfuscated the clear evidence of discontinuity and made Christianity an interloper in Israel's unique promises, the prime example being Catholicism.

A marked split with traditional Christendom, Classical Pauline Dispensationalism (JND) held that the covenants (including the briefly-mentioned "New Covenant") exclusively pertained to the earthly Elect Nation of Israel(1). Further, the Church/Body of Christ (whose advent was recorded at Acts 2) was the "heavenly people of God" a separate group having a level of discontinuity from Israel.

(1) See An Introduction to the NEW COVENANT, Christopher Cone, General Editor.

First, keep in mind that neither Dispensationalism nor Reformed/Calvinism fit neatly into tight boxes. There's a great deal of theological/philosophical diversity/variation in both realms. Clarity is important, so I'll strive to keep it as simple as possible.

The best approach to answering the question might be to mention what core beliefs they share in common, before proceeding to their CORE difference(s). (PS. I've spent nearly 55 years exploring these realms. When I reference "Dispensationalism," I historically trace the doctrinal distinctions to the extraordinary John Nelson Darby (JND) and his Classical Pauline view(s). The most definitive resources here are the extensive works of the late Roy A. Huebner.) Say what you will, but Darby was both a stalwart and a warrior for our Lord Jesus Christ.

COMMON: Both Reformed/Calvinism and Classical Pauline Dispensationalism share a belief in the Sovereignty of God (in contrast to the sovereignty of Man) and the epistemological foundation of the Inerrant Word of God--the 66 Books of the Bible. Both believe that Election and Salvation are based on God's Grace and Mercy, apart from ANY form of merit.

DIFFERENCE: Reformed/Calvinism follows traditional Christendom in the use of God's covenants made with earthly Israel to superimpose a forced continuity to the 66 books of Scripture. By contrast, Dispensationalism held this obfuscated the clear evidence of discontinuity and made Christianity an interloper in Israel's unique promises, the prime example being Catholicism.

A marked split with traditional Christendom, Classical Pauline Dispensationalism (JND) held that the covenants (including the briefly-mentioned "New Covenant") exclusively pertained to the earthly Elect Nation of Israel(1). Further, the Church/Body of Christ (whose advent was recorded in Acts 2) was the "heavenly people of God" and a separate group having a level of discontinuity from Israel.

(1) See An Introduction to the NEW COVENANT, Christopher Cone, General Editor.