diff --git a/apps/calculation/calculation.cpp b/apps/calculation/calculation.cpp
index a6d1f518d..b6f8c2d5d 100644
--- a/apps/calculation/calculation.cpp
+++ b/apps/calculation/calculation.cpp
@@ -15,7 +15,8 @@ Calculation::Calculation() :
   m_exactOutput(nullptr),
   m_exactOutputLayout(nullptr),
   m_approximateOutput(nullptr),
-  m_approximateOutputLayout(nullptr)
+  m_approximateOutputLayout(nullptr),
+  m_equalSign(EqualSign::Unknown)
 {
 }
 
@@ -142,6 +143,7 @@ void Calculation::tidy() {
     delete m_approximateOutputLayout;
   }
   m_approximateOutputLayout = nullptr;
+  m_equalSign = EqualSign::Unknown;
 }
 
 Expression * Calculation::exactOutput(Context * context) {
@@ -189,7 +191,10 @@ bool Calculation::shouldDisplayApproximateOutput(Context * context) {
   return input()->isApproximate(*context);
 }
 
-bool Calculation::exactAndApproximateDisplayedOutputsAreEqual(Poincare::Context * context) {
+Calculation::EqualSign Calculation::exactAndApproximateDisplayedOutputsAreEqual(Poincare::Context * context) {
+  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
@@ -198,9 +203,9 @@ bool Calculation::exactAndApproximateDisplayedOutputsAreEqual(Poincare::Context
    * are not identical. (For example, 0.000025 might be displayed "0.00003"
    * which requires in an approximative equal) */
   Expression * approximateOutput = Expression::ParseAndSimplify(buffer, *context);
-  bool isEqual = approximateOutput->isIdenticalTo(exactOutput(context));
+  m_equalSign = approximateOutput->isIdenticalTo(exactOutput(context)) ? EqualSign::Equal : EqualSign::Approximation;
   delete approximateOutput;
-  return isEqual;
+  return m_equalSign;
 }
 
 }
diff --git a/apps/calculation/calculation.h b/apps/calculation/calculation.h
index eaf4c6234..ff9b1c8cb 100644
--- a/apps/calculation/calculation.h
+++ b/apps/calculation/calculation.h
@@ -10,6 +10,11 @@ class CalculationStore;
 
 class Calculation {
 public:
+  enum class EqualSign : uint8_t {
+    Unknown,
+    Approximation,
+    Equal
+  };
   Calculation();
   ~Calculation(); // Delete expression and layout, if needed
   Calculation& operator=(const Calculation& other);
@@ -31,7 +36,7 @@ public:
   bool isEmpty();
   void tidy();
   bool shouldDisplayApproximateOutput(Poincare::Context * context);
-  bool exactAndApproximateDisplayedOutputsAreEqual(Poincare::Context * context);
+  EqualSign exactAndApproximateDisplayedOutputsAreEqual(Poincare::Context * context);
   constexpr static int k_printedExpressionSize = 2*::TextField::maxBufferSize();
 private:
   /* Buffers holding text expressions have to be longer than the text written
@@ -46,6 +51,7 @@ private:
   Poincare::ExpressionLayout * m_exactOutputLayout;
   Poincare::Expression * m_approximateOutput;
   Poincare::ExpressionLayout * m_approximateOutputLayout;
+  EqualSign m_equalSign;
 };
 
 }
diff --git a/apps/calculation/history_view_cell.cpp b/apps/calculation/history_view_cell.cpp
index a1f6881ee..c0546edd3 100644
--- a/apps/calculation/history_view_cell.cpp
+++ b/apps/calculation/history_view_cell.cpp
@@ -90,7 +90,7 @@ void HistoryViewCell::setCalculation(Calculation * calculation) {
    * outputView()->layoutSubviews() is going to fail. */
   Poincare::ExpressionLayout * outputExpressions[2] = {calculation->approximateOutputLayout(calculationApp->localContext()), calculation->shouldDisplayApproximateOutput(calculationApp->localContext()) ? nullptr : calculation->exactOutputLayout(calculationApp->localContext())};
   m_scrollableOutputView.outputView()->setExpressions(outputExpressions);
-  I18n::Message equalMessage = calculation->exactAndApproximateDisplayedOutputsAreEqual(calculationApp->localContext()) ? I18n::Message::Equal : I18n::Message::AlmostEqual;
+  I18n::Message equalMessage = calculation->exactAndApproximateDisplayedOutputsAreEqual(calculationApp->localContext()) == Calculation::EqualSign::Equal ? I18n::Message::Equal : I18n::Message::AlmostEqual;
   m_scrollableOutputView.outputView()->setEqualMessage(equalMessage);
 }