Restructured the project structure back to the way it was, there's no reasonable way to split the modules

src/NadekoBot/Modules/Utility/Calc/CalcCommands.cs

@@ -0,0 +1,48 @@
+#nullable disable
+using NCalc;
+using System.Reflection;
+
+namespace NadekoBot.Modules.Utility;
+
+public partial class Utility
+{
+    [Group]
+    public partial class CalcCommands : NadekoModule
+    {
+        [Cmd]
+        public async Task Calculate([Leftover] string expression)
+        {
+            var expr = new Expression(expression, EvaluateOptions.IgnoreCase | EvaluateOptions.NoCache);
+            expr.EvaluateParameter += Expr_EvaluateParameter;
+            var result = expr.Evaluate();
+            if (!expr.HasErrors())
+                await SendConfirmAsync("⚙ " + GetText(strs.result), result.ToString());
+            else
+                await SendErrorAsync("⚙ " + GetText(strs.error), expr.Error);
+        }
+
+        private static void Expr_EvaluateParameter(string name, ParameterArgs args)
+        {
+            switch (name.ToLowerInvariant())
+            {
+                case "pi":
+                    args.Result = Math.PI;
+                    break;
+                case "e":
+                    args.Result = Math.E;
+                    break;
+            }
+        }
+
+        [Cmd]
+        public async Task CalcOps()
+        {
+            var selection = typeof(Math).GetTypeInfo()
+                                        .GetMethods()
+                                        .DistinctBy(x => x.Name)
+                                        .Select(x => x.Name)
+                                        .Except(new[] { "ToString", "Equals", "GetHashCode", "GetType" });
+            await SendConfirmAsync(GetText(strs.calcops(prefix)), string.Join(", ", selection));
+        }
+    }
+}