diff --git a/src/h3lib/include/constants.h b/src/h3lib/include/constants.h
index db53adaab..fe84842a8 100644
--- a/src/h3lib/include/constants.h
+++ b/src/h3lib/include/constants.h
@@ -31,37 +31,43 @@
 #endif
 
 /** 2.0 * PI */
-#define M_2PI 6.28318530717958647692528676655900576839433L
+#define M_2PI 6.28318530717958647692528676655900576839433
 
 /** pi / 180 */
-#define M_PI_180 0.0174532925199432957692369076848861271111L
+#define M_PI_180 0.0174532925199432957692369076848861271111
 /** 180 / pi */
-#define M_180_PI 57.29577951308232087679815481410517033240547L
+#define M_180_PI 57.29577951308232087679815481410517033240547
 
 /** threshold epsilon */
-#define EPSILON 0.0000000000000001L
+#define EPSILON 0.0000000000000001
 /** sqrt(3) / 2.0 */
-#define M_SQRT3_2 0.8660254037844386467637231707529361834714L
+#define M_SQRT3_2 0.8660254037844386467637231707529361834714
 /** sin(60') */
 #define M_SIN60 M_SQRT3_2
+/** 1/sin(60') **/
+#define M_RSIN60 1.1547005383792515290182975610039149112953
+
+/** one third **/
+#define M_ONETHIRD 0.333333333333333333333333333333333333333
 
 /** rotation angle between Class II and Class III resolution axes
  * (asin(sqrt(3.0 / 28.0))) */
-#define M_AP7_ROT_RADS 0.333473172251832115336090755351601070065900389L
+#define M_AP7_ROT_RADS 0.333473172251832115336090755351601070065900389
 
 /** sin(M_AP7_ROT_RADS) */
-#define M_SIN_AP7_ROT 0.3273268353539885718950318L
+#define M_SIN_AP7_ROT 0.3273268353539885718950318
 
 /** cos(M_AP7_ROT_RADS) */
-#define M_COS_AP7_ROT 0.9449111825230680680167902L
+#define M_COS_AP7_ROT 0.9449111825230680680167902
 
 /** earth radius in kilometers using WGS84 authalic radius */
-#define EARTH_RADIUS_KM 6371.007180918475L
+#define EARTH_RADIUS_KM 6371.007180918475
 
 /** scaling factor from hex2d resolution 0 unit length
  * (or distance between adjacent cell center points
  * on the plane) to gnomonic unit length. */
-#define RES0_U_GNOMONIC 0.38196601125010500003L
+#define RES0_U_GNOMONIC 0.38196601125010500003
+#define INV_RES0_U_GNOMONIC 2.61803398874989588842
 
 /** max H3 resolution; H3 version 1 has 16 resolutions, numbered 0 through 15 */
 #define MAX_H3_RES 15
diff --git a/src/h3lib/lib/coordijk.c b/src/h3lib/lib/coordijk.c
index d4276001d..7f9ff7cb5 100644
--- a/src/h3lib/lib/coordijk.c
+++ b/src/h3lib/lib/coordijk.c
@@ -66,7 +66,7 @@ void _hex2dToCoordIJK(const Vec2d *v, CoordIJK *h) {
     a2 = fabsl(v->y);
 
     // first do a reverse conversion
-    x2 = a2 / M_SIN60;
+    x2 = a2 * M_RSIN60;
     x1 = a1 + x2 / 2.0;
 
     // check if we have the center of a hex
diff --git a/src/h3lib/lib/faceijk.c b/src/h3lib/lib/faceijk.c
index aee1d92a7..133b5f4bc 100644
--- a/src/h3lib/lib/faceijk.c
+++ b/src/h3lib/lib/faceijk.c
@@ -32,8 +32,9 @@
 #include "latLng.h"
 #include "vec3d.h"
 
-/** square root of 7 */
+/** square root of 7 and inverse square root of 7 */
 #define M_SQRT7 2.6457513110645905905016157536392604257102
+#define M_RSQRT7 0.37796447300922722721451653623418006081576
 
 /** @brief icosahedron face centers in lat/lng radians */
 const LatLng faceCenterGeo[NUM_ICOSA_FACES] = {
@@ -446,12 +447,12 @@ void _hex2dToGeo(const Vec2d *v, int face, int res, int substrate, LatLng *g) {
     double theta = atan2(v->y, v->x);
 
     // scale for current resolution length u
-    for (int i = 0; i < res; i++) r /= M_SQRT7;
+    for (int i = 0; i < res; i++) r *= M_RSQRT7;
 
     // scale accordingly if this is a substrate grid
     if (substrate) {
-        r /= 3.0;
-        if (isResolutionClassIII(res)) r /= M_SQRT7;
+        r *= M_ONETHIRD;
+        if (isResolutionClassIII(res)) r *= M_RSQRT7;
     }
 
     r *= RES0_U_GNOMONIC;