diff --git a/native/jni/src/proximity_info.cpp b/native/jni/src/proximity_info.cpp
index d812745..81eb0b3 100644
--- a/native/jni/src/proximity_info.cpp
+++ b/native/jni/src/proximity_info.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <cstring>
+#include <cmath>
 
 #define LOG_TAG "LatinIME: proximity_info.cpp"
 
@@ -59,6 +60,7 @@
           CELL_HEIGHT((keyboardHeight + gridHeight - 1) / gridHeight),
           KEY_COUNT(min(keyCount, MAX_KEY_COUNT_IN_A_KEYBOARD)),
           KEYBOARD_WIDTH(keyboardWidth), KEYBOARD_HEIGHT(keyboardHeight),
+          KEYBOARD_HYPOTENUSE(hypotf(KEYBOARD_WIDTH, KEYBOARD_HEIGHT)),
           HAS_TOUCH_POSITION_CORRECTION_DATA(keyCount > 0 && keyXCoordinates && keyYCoordinates
                   && keyWidths && keyHeights && keyCharCodes && sweetSpotCenterXs
                   && sweetSpotCenterYs && sweetSpotRadii),
diff --git a/native/jni/src/proximity_info.h b/native/jni/src/proximity_info.h
index d42c723..ee79367 100644
--- a/native/jni/src/proximity_info.h
+++ b/native/jni/src/proximity_info.h
@@ -62,6 +62,7 @@
     int getGridHeight() const { return GRID_HEIGHT; }
     int getKeyboardWidth() const { return KEYBOARD_WIDTH; }
     int getKeyboardHeight() const { return KEYBOARD_HEIGHT; }
+    float getKeyboardHypotenuse() const { return KEYBOARD_HYPOTENUSE; }
 
     int getKeyCenterXOfCodePointG(int charCode) const;
     int getKeyCenterYOfCodePointG(int charCode) const;
@@ -97,6 +98,7 @@
     const int KEY_COUNT;
     const int KEYBOARD_WIDTH;
     const int KEYBOARD_HEIGHT;
+    const float KEYBOARD_HYPOTENUSE;
     const bool HAS_TOUCH_POSITION_CORRECTION_DATA;
     char mLocaleStr[MAX_LOCALE_STRING_LENGTH];
     int *mProximityCharsArray;