diff --git a/math/calc/Makefile b/math/calc/Makefile
index 7ff0e0652d04..b4ce6b597e28 100644
--- a/math/calc/Makefile
+++ b/math/calc/Makefile
@@ -1,8 +1,8 @@
 DISTNAME=	calc-2.9.3t6
 MASTER_SITES=	ftp://ftp.cs.uni-sb.de/pub/misc/4.4BSD-Lite/contrib/
 
-.include <bsd.port.mk>
-
-
 pre-install:
-	@mkdir /usr/local/lib
\ No newline at end of file
+	@mkdir -p ${PREFIX}/lib/calc/help
+	@mkdir -p ${PREFIX}/man/man1
+
+.include <bsd.port.mk>
diff --git a/math/calc/scripts/configure b/math/calc/scripts/configure
index 1e3605568218..a6483fb5295c 100644
--- a/math/calc/scripts/configure
+++ b/math/calc/scripts/configure
@@ -1,10 +1,12 @@
 #!/bin/sh
 
-F=${WRKSRC}/Makefile
+PREFIX=${PREFIX:-/usr/local}
+
+F=$WRKSRC/Makefile
 
 chmod +w $F || exit 1;
 
-echo "BINDIR= /usr/local/bin" >> $F || exit 1;
-echo "TOPDIR= /usr/local/lib" >> $F 
-echo "MANDIR=/usr/local/man/man1" >> $F
+echo "BINDIR= $PREFIX/bin" >> $F || exit 1;
+echo "TOPDIR= $PREFIX/lib" >> $F 
+echo "MANDIR= $PREFIX/man/man1" >> $F
 echo "CCOPT= -Wall -Wno-implicit -Wno-comment" >> $F
\ No newline at end of file