diff --git a/indra/llimage/llimagej2c.cpp b/indra/llimage/llimagej2c.cpp
index e01e3adce..4daf0ec1f 100644
--- a/indra/llimage/llimagej2c.cpp
+++ b/indra/llimage/llimagej2c.cpp
@@ -381,7 +381,13 @@ S32 LLImageJ2C::calcDataSize(S32 discard_level)
 	static const LLCachedControl<bool> legacy_size("SianaLegacyJ2CSize", false);
 	
 	if (legacy_size) {
-		return calcDataSizeJ2C(getWidth(), getHeight(), getComponents(), discard_level, mRate);
+		static const LLCachedControl<F32> exponent("SianaJ2CSizeExponent", 1.0f);
+		static const LLCachedControl<S32> offset("SianaJ2CSizeOffset", 0);
+		
+		S32 size = calcDataSizeJ2C(getWidth(), getHeight(), getComponents(), discard_level, mRate);
+		S32 size_d0 = calcDataSizeJ2C(getWidth(), getHeight(), getComponents(), discard_level, mRate);
+		
+		return pow(size/size_d0, exponent)*size_d0 + offset;
 	}
 
 	discard_level = llclamp(discard_level, 0, MAX_DISCARD_LEVEL);
diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 07da20141..dc4aeef4a 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -37,6 +37,29 @@
     </array>
   </map>
 
+	<key>SianaJ2CSizeExponent</key>
+	<map>
+		<key>Comment</key>
+		<string>Exponent of size estimator. Should be between 0.0 and 1.0</string>
+		<key>Persist</key>
+		<integer>1</integer>
+		<key>Type</key>
+		<string>F32</string>
+		<key>Value</key>
+		<real>0.5</real>
+	</map>
+	<key>SianaJ2CSizeOffset</key>
+	<map>
+		<key>Comment</key>
+		<string>Number of bytes to add to size estimator.</string>
+		<key>Persist</key>
+		<integer>1</integer>
+		<key>Type</key>
+		<string>S32</string>
+		<key>Value</key>
+		<integer>100</integer>
+	</map>
+
 	<key>SianaLegacyJ2CSize</key>
 	<map>
 		<key>Comment</key>