diff --git a/gprMax/constants.pxd b/gprMax/constants.pxd
index 29b835ff..73984bbb 100644
--- a/gprMax/constants.pxd
+++ b/gprMax/constants.pxd
@@ -25,5 +25,10 @@ cimport numpy as np
 #   Fractal and dispersive coefficient arrays use complex numbers (complextype) which are represented as two floats
 #   Main field arrays use floats (floattype) and complex numbers (complextype)
 
+# Single precision
 ctypedef np.float32_t floattype_t
 ctypedef np.complex64_t complextype_t
+
+# Double precision
+#ctypedef np.float64_t floattype_t
+#ctypedef np.complex128_t complextype_t
diff --git a/gprMax/constants.py b/gprMax/constants.py
index f56a9556..7d9996a5 100644
--- a/gprMax/constants.py
+++ b/gprMax/constants.py
@@ -30,5 +30,20 @@ z0 = np.sqrt(m0 / e0)
 #   Fractal and dispersive coefficient arrays use complex numbers (complextype) which are represented as two floats
 #   Main field arrays use floats (floattype) and complex numbers (complextype)
 
+# Single precision
+# For numpy arrays
 floattype = np.float32
 complextype = np.complex64
+
+# For C (CUDA) arrays
+cfloattype = 'float'
+ccomplextype = 'pycuda::complex<float>'
+
+# Double precision
+# For numpy arrays
+#floattype = np.float64
+#complextype = np.complex128
+
+# For C (CUDA) arrays
+#cfloattype = 'double'
+#ccomplextype = 'pycuda::complex<double>'