diff --git a/pyModeS/c_common.pxd b/pyModeS/c_common.pxd
index fe8892e..de13840 100644
--- a/pyModeS/c_common.pxd
+++ b/pyModeS/c_common.pxd
@@ -5,7 +5,8 @@ cdef unsigned char int_to_char(unsigned char i)
 
 cpdef str hex2bin(str hexstr)
 cpdef long bin2int(str binstr)
-cpdef long hex2int(str binstr)
+cpdef long hex2int(str hexstr)
+cpdef str bin2hex(str binstr)
 
 cpdef unsigned char df(str msg)
 cpdef long crc(str msg, bint encode=*)
diff --git a/pyModeS/c_common.pyx b/pyModeS/c_common.pyx
index c92bd70..77dad81 100644
--- a/pyModeS/c_common.pyx
+++ b/pyModeS/c_common.pyx
@@ -66,6 +66,11 @@ cpdef long hex2int(str hexstr):
         cumul = 16*cumul + char_to_int(v_hexstr[i])
     return cumul
 
+@cython.boundscheck(False)
+cpdef str bin2hex(str binstr):
+    return "{0:X}".format(int(binstr, 2))
+
+
 @cython.boundscheck(False)
 cpdef unsigned char df(str msg):
     """Decode Downlink Format vaule, bits 1 to 5."""
diff --git a/pyModeS/common.py b/pyModeS/common.py
index cb2df95..d1a4c81 100644
--- a/pyModeS/common.py
+++ b/pyModeS/common.py
@@ -19,6 +19,11 @@ def bin2int(binstr):
     return int(binstr, 2)
 
 
+def bin2hex(binstr):
+    """Convert a binary string to hexdecimal string."""
+    return "{0:X}".format(int(binstr, 2))
+
+
 def df(msg):
     """Decode Downlink Format value, bits 1 to 5."""
     dfbin = hex2bin(msg[:2])
diff --git a/tests/test_c_common.py b/tests/test_c_common.py
index 71cc3f8..d55b588 100644
--- a/tests/test_c_common.py
+++ b/tests/test_c_common.py
@@ -2,7 +2,9 @@ try:
     from pyModeS.decoder import c_common as common
 
     def test_conversions():
-        assert common.hex2bin("6E406B") == "011011100100000001101011"
+        assert common.hex2bin("6E") == "01101110"
+        assert common.bin2hex("01101110") == "6E"
+        assert common.bin2hex("1101110") == "6E"
 
     def test_crc_decode():
 
diff --git a/tests/test_common.py b/tests/test_common.py
index 6149ca4..e9e871c 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -2,7 +2,9 @@ from pyModeS import common
 
 
 def test_conversions():
-    assert common.hex2bin("6E406B") == "011011100100000001101011"
+    assert common.hex2bin("6E") == "01101110"
+    assert common.bin2hex("01101110") == "6E"
+    assert common.bin2hex("1101110") == "6E"
 
 
 def test_crc_decode():