diff --git a/monero/numbers.py b/monero/numbers.py
new file mode 100644
index 0000000..7bd6ea8
--- /dev/null
+++ b/monero/numbers.py
@@ -0,0 +1,9 @@
+from decimal import Decimal
+
+PICONERO = Decimal('0.000000000001')
+
+def to_atomic(amount):
+    return int(amount * 10**12)
+
+def from_atomic(amount):
+    return (Decimal(amount) * PICONERO).quantize(PICONERO)
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..aad4419
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1,2 @@
+from .address import AddressTestCase, TestnetAddressTestCase
+from .numbers import NumbersTestCase
diff --git a/test.py b/tests/address.py
similarity index 100%
rename from test.py
rename to tests/address.py
diff --git a/tests/numbers.py b/tests/numbers.py
new file mode 100644
index 0000000..5f7c8dd
--- /dev/null
+++ b/tests/numbers.py
@@ -0,0 +1,16 @@
+from decimal import Decimal
+import unittest
+
+from monero.numbers import to_atomic, from_atomic
+
+class NumbersTestCase(unittest.TestCase):
+    def test_simple_numbers(self):
+        self.assertEqual(to_atomic(Decimal('0')), 0)
+        self.assertEqual(from_atomic(0), Decimal('0'))
+        self.assertEqual(to_atomic(Decimal('1')), 1000000000000)
+        self.assertEqual(from_atomic(1000000000000), Decimal('1'))
+        self.assertEqual(to_atomic(Decimal('0.000000000001')), 1)
+        self.assertEqual(from_atomic(1), Decimal('0.000000000001'))
+
+    def test_rounding(self):
+        self.assertEqual(to_atomic(Decimal('1.0000000000004')), 1000000000000)