diff --git a/libretroshare/src/util/rsbase64.cc b/libretroshare/src/util/rsbase64.cc
index 72ea119e8..f62c40cef 100644
--- a/libretroshare/src/util/rsbase64.cc
+++ b/libretroshare/src/util/rsbase64.cc
@@ -21,8 +21,6 @@
  *                                                                             *
  *******************************************************************************/
 
-#include <cmath>
-
 #include "util/rsbase64.h"
 #include "util/rsdebug.h"
 
@@ -144,9 +142,10 @@
 /*static*/ size_t RsBase64::encodedSize(size_t decodedSize, bool padding)
 {
 	if(!decodedSize) return 0;
-	if(padding) return 4 * (decodedSize + 2) / 3;
-	return static_cast<size_t>(
-	            std::ceil(4L * static_cast<double>(decodedSize) / 3L) );
+
+	// Thanks https://stackoverflow.com/a/45401395
+	if(padding) return ceilDivision(decodedSize, 3) * 4;
+	return ceilDivision(decodedSize * 8, 6);
 }
 
 /*static*/ std::tuple<size_t, std::error_condition> RsBase64::decodedSize(
diff --git a/libretroshare/src/util/rsbase64.h b/libretroshare/src/util/rsbase64.h
index 0715b15ae..819870089 100644
--- a/libretroshare/src/util/rsbase64.h
+++ b/libretroshare/src/util/rsbase64.h
@@ -137,4 +137,8 @@ private:
 	 */
 	static inline bool isBase64Char(char c)
 	{ return rDict[static_cast<uint8_t>(c)] >= 0; }
+
+	/** Perform ceil division without floating point operations */
+	static inline size_t ceilDivision(size_t dividend, size_t divisor)
+	{ return (dividend + divisor - 1) / divisor; }
 };