diff --git a/apps/calculation/calculation.cpp b/apps/calculation/calculation.cpp
index f51dd5eae..7aae60e23 100644
--- a/apps/calculation/calculation.cpp
+++ b/apps/calculation/calculation.cpp
@@ -194,16 +194,7 @@ Calculation::EqualSign Calculation::exactAndApproximateDisplayedOutputsAreEqual(
   if (m_equalSign != EqualSign::Unknown) {
     return m_equalSign;
   }
-  char buffer[k_printedExpressionSize];
-  approximateOutput(context)->writeTextInBuffer(buffer, k_printedExpressionSize, Preferences::sharedPreferences()->numberOfSignificantDigits());
-  /* Warning: we cannot use directly the m_approximateOutputText but we have to
-   * re-serialize the approximateOutput because the number of stored
-   * significative numbers and the number of displayed significative numbers
-   * are not identical. (For example, 0.000025 might be displayed "0.00003"
-   * which requires in an approximative equal) */
-  Expression * approximateOutput = Expression::ParseAndSimplify(buffer, *context);
-  m_equalSign = approximateOutput->isIdenticalTo(exactOutput(context)) ? EqualSign::Equal : EqualSign::Approximation;
-  delete approximateOutput;
+  m_equalSign = exactOutput(context)->isEqualToItsApproximationLayout(approximateOutput(context), k_printedExpressionSize, Preferences::sharedPreferences()->numberOfSignificantDigits(), *context) ? EqualSign::Equal : EqualSign::Approximation;
   return m_equalSign;
 }
 
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 24e74a8c4..508d6cbb4 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -245,6 +245,7 @@ public:
      * order on expresssions. */
     return SimplificationOrder(this, e, true) == 0;
   }
+  bool isEqualToItsApproximationLayout(Expression * approximation, int bufferSize, int numberOfSignificantDigits, Context & context);
 
   /* Layout Engine */
   ExpressionLayout * createLayout(PrintFloat::Mode floatDisplayMode = PrintFloat::Mode::Default, ComplexFormat complexFormat = ComplexFormat::Default) const; // Returned object must be deleted
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index e761e2532..70200b929 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -325,6 +325,21 @@ int Expression::SimplificationOrder(const Expression * e1, const Expression * e2
   }
 }
 
+bool Expression::isEqualToItsApproximationLayout(Expression * approximation, int bufferSize, int numberOfSignificantDigits, Context & context) {
+  char buffer[bufferSize];
+  approximation->writeTextInBuffer(buffer, bufferSize, numberOfSignificantDigits);
+  /* Warning: we cannot use directly the the approximate expression but we have
+   * to re-serialize it because the number of stored significative
+   * numbers and the number of displayed significative numbers might not be
+   * identical. (For example, 0.000025 might be displayed "0.00003" and stored
+   * as Decimal(0.000025) and isEqualToItsApproximationLayout should return
+   * false) */
+  Expression * approximateOutput = Expression::ParseAndSimplify(buffer, context);
+  bool equal = isIdenticalTo(approximateOutput);
+  delete approximateOutput;
+  return equal;
+}
+
 /* Layout */
 
 ExpressionLayout * Expression::createLayout(PrintFloat::Mode floatDisplayMode, ComplexFormat complexFormat) const {