diff --git a/poincare/include/poincare/zoom.h b/poincare/include/poincare/zoom.h
index 591e64b20..dae416203 100644
--- a/poincare/include/poincare/zoom.h
+++ b/poincare/include/poincare/zoom.h
@@ -67,6 +67,7 @@ private:
    * an asymptote, by recursively computing the slopes. In case of an extremum,
    * the slope should taper off toward the center. */
   static bool IsConvexAroundExtremum(ValueAtAbscissa evaluation, float x1, float x2, float x3, float y1, float y2, float y3, Context * context, const void * auxiliary, int iterations = 3);
+  static void NextUnit(float * mantissa, float * exponent);
 };
 
 }
diff --git a/poincare/src/zoom.cpp b/poincare/src/zoom.cpp
index b9683b6f2..20cf54bb1 100644
--- a/poincare/src/zoom.cpp
+++ b/poincare/src/zoom.cpp
@@ -371,4 +371,21 @@ bool Zoom::IsConvexAroundExtremum(ValueAtAbscissa evaluation, float x1, float x2
   return true;
 }
 
+void Zoom::NextUnit(float * mantissa, float * exponent) {
+  if (*mantissa == k_smallUnitMantissa) {
+    *mantissa = k_mediumUnitMantissa;
+    return;
+  }
+  if (*mantissa == k_mediumUnitMantissa) {
+    *mantissa = k_largeUnitMantissa;
+    return;
+  }
+  if (*mantissa == k_largeUnitMantissa) {
+    *mantissa = k_smallUnitMantissa;
+    *exponent = 10.f * *exponent;
+    return;
+  }
+  assert(false);
+}
+
 }