diff --git a/balance_service/tests.py b/balance_service/tests.py
new file mode 100644
index 00000000..c7d8f5a4
--- /dev/null
+++ b/balance_service/tests.py
@@ -0,0 +1,118 @@
+from django.test import TestCase
+from django.utils import timezone
+from allocations.models import Charge
+from projects.models import Project
+from django.contrib.auth import get_user_model
+from unittest.mock import patch
+
+from .utils.su_calculators import get_used_sus, get_total_sus, get_active_allocation, project_balances, calculate_user_total_su_usage
+
+class SUCalculatorsTest(TestCase):
+    def setUp(self):
+        # Set up data for the tests
+        User = get_user_model()
+        self.now = timezone.now()
+        self.test_requestor = User.objects.create_user(
+            username="test_requestor",
+            password="test_password",
+        )
+        self.test_user_2 = User.objects.create_user(
+            username="test_user_2",
+            password="test_password",
+        )
+
+        self.project = Project.objects.create(
+            tag=None,
+            automatically_tagged=False,
+            description="This is a test project for allocations.",
+            pi=self.test_requestor,
+            title="Test Project",
+            nickname="test_project",
+            charge_code="TEST123"
+        )
+        self.allocation = self.project.allocations.create(
+            project=self.project,
+            status="active",
+            justification="This is a test allocation.",
+            requestor=self.test_requestor,
+            date_requested=self.now,
+            decision_summary="Test decision summary.",
+            reviewer=self.test_requestor,
+            date_reviewed=self.now,
+            expiration_date=self.now + timezone.timedelta(days=30),
+            su_requested=100.0,
+            start_date=self.now,
+            su_allocated=50.0,
+            su_used=25.0,
+            balance_service_version=2,
+        )
+        # Charge is 1/3 through
+        self.charge = Charge.objects.create(
+            allocation=self.allocation,
+            user=self.test_requestor,
+            region_name="DEV@UC",
+            resource_id="123",
+            resource_type="baremetal",
+            start_time=self.now - timezone.timedelta(hours=3),
+            end_time=self.now + timezone.timedelta(hours=6),
+            hourly_cost=2.0,
+        )
+        Charge.objects.create(
+            allocation=self.allocation,
+            user=self.test_requestor,
+            region_name="DEV@UC",
+            resource_id="123",
+            resource_type="baremetal",
+            start_time=self.now + timezone.timedelta(hours=1),
+            end_time=self.now + timezone.timedelta(hours=2),
+            hourly_cost=3.0,
+        )
+        Charge.objects.create(
+            allocation=self.allocation,
+            user=self.test_user_2,
+            region_name="DEV@UC",
+            resource_id="123",
+            resource_type="baremetal",
+            start_time=self.now - timezone.timedelta(hours=2),
+            end_time=self.now + timezone.timedelta(hours=2),
+            hourly_cost=5.0,
+        )
+
+    @patch('django.utils.timezone.now')  # Mocking timezone.now()
+    def test_get_used_sus(self, mock_now):
+        mock_now.return_value = self.now
+        # Test the get_used_sus function
+        used_sus = get_used_sus(self.charge)
+        self.assertAlmostEqual(used_sus, 6.0, places=2)
+
+    def test_get_total_sus(self):
+        # Test the get_total_sus function
+        total_sus = get_total_sus(self.charge)
+        self.assertAlmostEqual(total_sus, 18.0, places=2)
+
+    def test_get_active_allocation(self):
+        # Test the get_active_allocation function
+        active_allocation = get_active_allocation(self.project)
+        self.assertIsNotNone(active_allocation)
+        self.assertEqual(active_allocation.status, "active")
+
+    @patch('django.utils.timezone.now')  # Mocking timezone.now()
+    def test_project_balances(self, mock_now):
+        mock_now.return_value = self.now
+        # Test the project_balances function
+        balances = project_balances([self.project.id])
+        self.assertEqual(len(balances), 1)
+        balance = balances[0]
+        self.assertEqual(balance['charge_code'], 'TEST123')
+        self.assertAlmostEqual(balance['used'], 16.0, places=2)
+        self.assertAlmostEqual(balance['total'], 41.0, places=2)
+        self.assertAlmostEqual(balance['allocated'], 50)
+        self.assertAlmostEqual(balance['encumbered'], 25.0, places=2)
+
+    @patch('django.utils.timezone.now')  # Mocking timezone.now()
+    def test_calculate_user_total_su_usage(self, mock_now):
+        mock_now.return_value = self.now
+        # Test calculate_user_total_su_usage function
+        user = self.charge.user  # Assuming a user is associated with the charge
+        total_su_usage = calculate_user_total_su_usage(user, self.project)
+        self.assertAlmostEqual(total_su_usage, 21.0, places=2)
diff --git a/balance_service/utils/su_calculators.py b/balance_service/utils/su_calculators.py
index c6345e8a..51098122 100644
--- a/balance_service/utils/su_calculators.py
+++ b/balance_service/utils/su_calculators.py
@@ -72,9 +72,9 @@ def project_balances(project_ids) -> "list[dict]":
             {
                 "id": project.id,
                 "charge_code": project.charge_code,
-                "used": used_sus,
-                "total": total_sus,
-                "encumbered": total_sus - used_sus,
+                "used": used_sus, # how much they have used
+                "total": total_sus, # how much they have used + pending use
+                "encumbered": total_sus - used_sus, # pending use
                 "allocated": allocated_sus,
             }
         )