diff --git a/src/material.cpp b/src/material.cpp
index 2403a55fb9..ec55bfb081 100644
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -1101,9 +1101,9 @@ pyne::comp_map pyne::Material::decay_heat() {
   pyne::comp_map dh;
   double masspermole = mass * pyne::N_A;
   for (pyne::comp_iter i = comp.begin(); i != comp.end(); ++i) {
-    dh[i->first] = pyne::MeV_per_MJ * masspermole * (i->second) * \
+    dh[i->first] = masspermole * (i->second) * \
                    decay_const(i->first) * q_val(i->first) / \
-                   atomic_mass(i->first);
+                   atomic_mass(i->first) / pyne::MeV_per_MJ;
   }
   return dh;
 }
diff --git a/src/material.h b/src/material.h
index bf642ff767..dc9ab50c0e 100644
--- a/src/material.h
+++ b/src/material.h
@@ -233,7 +233,8 @@ namespace pyne
     /// nuclide's mass, decay_const, and atmoic_mass. 
     comp_map activity();
     /// Calculates the decay heat of a material based on the composition and
-    /// each nuclide's mass, q_val, decay_const, and atomic_mass.
+    /// each nuclide's mass, q_val, decay_const, and atomic_mass. This assumes
+    /// input mass of grams. Return values is in mega joules. 
     comp_map decay_heat();
     /// Caclulates the dose per gram using the composition of the the
     /// material, the dose type desired, and the source for dose factors