diff --git a/src/app/container/calculator.cpp b/src/app/container/calculator.cpp
index 4b8e56b6c..df87bea96 100644
--- a/src/app/container/calculator.cpp
+++ b/src/app/container/calculator.cpp
@@ -35,7 +35,17 @@ int Calculator::iVal = -1;
 
 //---------------------------------------------------------------------------------------------------------------------
 /**
- * @brief Calculator class constructor.
+ * @brief Calculator class constructor. Make easy initialization math parser.
+ *
+ * This constructor hide initialization variables, operators, character sets.
+ * Use this constuctor for evaluation formula. All formulas must be converted to internal look.
+ * Example:
+ *
+ * const QString formula = qApp->FormulaFromUser(edit->text());
+ * Calculator *cal = new Calculator(data);
+ * const qreal result = cal->EvalFormula(formula);
+ * delete cal;
+ *
  * @param data pointer to a variable container.
  */
 Calculator::Calculator(const VContainer *data)
@@ -56,6 +66,21 @@ Calculator::Calculator(const VContainer *data)
 }
 
 //---------------------------------------------------------------------------------------------------------------------
+/**
+ * @brief Calculator class constructor. Make easy initialization math parser.
+ *
+ * This constructor hide initialization variables, operators, character sets.
+ * Use this constuctor to get tokens from formula. All formulas must be converted to external look.
+ * Example:
+ *
+ * Calculator *cal = new Calculator(formula, false);
+ * tokens = cal->GetTokens();
+ * numbers = cal->GetNumbers();
+ * delete cal;
+ *
+ * @param data pointer to a variable container.
+ * @param fromUser true if we parse formula from user
+ */
 Calculator::Calculator(const QString &formula, bool fromUser)
     :QmuParser(), vVarVal(nullptr)
 {
@@ -97,7 +122,8 @@ Calculator::Calculator(const QString &formula, bool fromUser)
     }
 
     SetExpr(formula);
-    Eval();//Need run for making tokens
+    //Need run for making tokens. Don't catch exception here, because it will show us in dialog that formula has error.
+    Eval();
 }
 
 Calculator::~Calculator()
@@ -240,6 +266,7 @@ void Calculator::InitVariables(const VContainer *data)
     }
 }
 
+//---------------------------------------------------------------------------------------------------------------------
 void Calculator::InitCharacterSets()
 {
     //String with all unique symbols for supported alpabets.
diff --git a/src/app/container/calculator.h b/src/app/container/calculator.h
index 2961f6498..f9eb9e297 100644
--- a/src/app/container/calculator.h
+++ b/src/app/container/calculator.h
@@ -34,6 +34,25 @@
 #include "../../libs/qmuparser/qmuparser.h"
 using namespace qmu;
 
+/**
+ * @brief The Calculator class for calculation formula.
+ *
+ * Main purpose make easy evaluate value of formula and get tokens.
+ * Note. If created to many parser for different purpes in the same time parser can work wrong.
+ * Example:
+ * DialogEditWrongFormula *dialog = new DialogEditWrongFormula(data);
+ * dialog->setFormula(formula);
+ * if (dialog->exec() == QDialog::Accepted)
+ * {
+ *     formula = dialog->getFormula();
+ *     //Need delete dialog here because parser in dialog don't allow use correct separator for parsing here.
+ *     //Don't know why.
+ *     delete dialog;
+ *     Calculator *cal = new Calculator(data);
+ *     result = cal->EvalFormula(formula);
+ *     delete cal;//Here can be memory leak, but dialog already check this formula and probability very low.
+ * }
+ */
 class Calculator:public QmuParser
 {
 public:
diff --git a/src/app/tools/drawTools/vdrawtool.cpp b/src/app/tools/drawTools/vdrawtool.cpp
index 457de4522..e6637040d 100644
--- a/src/app/tools/drawTools/vdrawtool.cpp
+++ b/src/app/tools/drawTools/vdrawtool.cpp
@@ -59,8 +59,6 @@ VDrawTool::~VDrawTool()
     delete dialog;
 }
 
-
-
 //---------------------------------------------------------------------------------------------------------------------
 /**
  * @brief ShowTool  highlight tool.