diff --git a/exercise_utils.py b/exercise_utils.py
new file mode 100644
index 0000000..53d343c
--- /dev/null
+++ b/exercise_utils.py
@@ -0,0 +1,32 @@
+from collections import defaultdict
+
+
+names = [
+        'target',
+        'synergist',
+        'stabilizer',
+        'dynamic stabilizer',
+        'antagonist stabilizer'
+]
+percentages = {
+        names[0]: 75 * 0.01,
+        names[1]: 50 * 0.01,
+        names[2]: 5 * 0.01,
+        names[3]: 1 * 0.01,
+        names[4]: 1 * 0.01
+}
+
+
+def formula(exercise, custom_perc=dict()):
+    muscle_perc = defaultdict(int)
+
+    for name in names:
+
+        for muscle in exercise[name]:
+            if muscle in custom_perc:
+                if muscle_perc[muscle] == 0:
+                    muscle_perc[muscle] += custom_perc[name]
+            else:
+                muscle_perc[muscle] += percentages[name]
+
+    return muscle_perc