diff --git a/ChangeLog b/ChangeLog
index 3c2ea093..069101f6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,7 @@
 - cast to unsigned int now removes <0 values
 - vips7 interface to openslide now supports :,level,associated options
 - make vips8 cache smaller
+- more accurate progress reporting
 
 13/3/12 started 7.28.2
 - xres/yres tiffsave args were broken
diff --git a/libvips/include/vips/image.h b/libvips/include/vips/image.h
index cd5e1d44..e93d3e3c 100644
--- a/libvips/include/vips/image.h
+++ b/libvips/include/vips/image.h
@@ -476,7 +476,7 @@ int vips_image_written( VipsImage *image );
 void vips_image_invalidate_all( VipsImage *image );
 
 void vips_image_preeval( VipsImage *image );
-void vips_image_eval( VipsImage *image, int w, int h );
+void vips_image_eval( VipsImage *image, guint64 processed );
 void vips_image_posteval( VipsImage *image );
 void vips_image_set_progress( VipsImage *image, gboolean progress );
 
diff --git a/libvips/iofuncs/image.c b/libvips/iofuncs/image.c
index 0f40aa79..de8c2f99 100644
--- a/libvips/iofuncs/image.c
+++ b/libvips/iofuncs/image.c
@@ -1092,8 +1092,8 @@ vips_progress_add( VipsImage *image )
 	return( 0 );
 }
 
-void
-vips_progress_update( VipsProgress *progress, int w, int h )
+static void
+vips_progress_update( VipsProgress *progress, guint64 processed )
 {
 	float prop;
 
@@ -1102,11 +1102,11 @@ vips_progress_update( VipsProgress *progress, int w, int h )
 	g_assert( progress );
 
 	progress->run = g_timer_elapsed( progress->start, NULL );
-	progress->npels += w * h;
+	progress->npels = processed;
 	prop = (float) progress->npels / (float) progress->tpels;
 	progress->percent = 100 * prop;
 
-	/* Don't estiomate eta until we are 10% in.
+	/* Don't estimate eta until we are 10% in.
 	 */
 	if( prop > 0.1 ) 
 		progress->eta = (1.0 / prop) * progress->run - progress->run;
@@ -1135,10 +1135,10 @@ vips_image_preeval( VipsImage *image )
 	}
 }
 
-/* Another w * h pixels have been processed.
+/* Updated the number of pixels that have been processed.
  */
 void
-vips_image_eval( VipsImage *image, int w, int h )
+vips_image_eval( VipsImage *image, guint64 processed )
 {
 	if( image->progress_signal ) {
 		VIPS_DEBUG_MSG( "vips_image_eval: %p\n", image );
@@ -1146,7 +1146,7 @@ vips_image_eval( VipsImage *image, int w, int h )
 		g_assert( vips_object_sanity( 
 			VIPS_OBJECT( image->progress_signal ) ) );
 
-		vips_progress_update( image->time, w, h );
+		vips_progress_update( image->time, processed );
 
 		/* For vips7 compat, update the ->time on the signalling image
 		 * too, even though it may have a different width/height to
@@ -1154,7 +1154,7 @@ vips_image_eval( VipsImage *image, int w, int h )
 		 */
 		if( image->progress_signal->time != image->time )
 			vips_progress_update( image->progress_signal->time, 
-				w, h );	
+				processed );
 
 		g_signal_emit( image->progress_signal, 
 			vips_image_signals[SIG_EVAL], 0, image->time );
@@ -1878,7 +1878,7 @@ vips_image_write_line( VipsImage *image, int ypos, VipsPel *linebuffer )
 
 	/* Trigger evaluation callbacks for this image.
 	 */
-	vips_image_eval( image, image->Xsize, 1 );
+	vips_image_eval( image, ypos * image->Xsize );
 	if( vips_image_get_kill( image ) )
 		return( -1 );
 
diff --git a/libvips/iofuncs/sink.c b/libvips/iofuncs/sink.c
index 1f05ed91..b34e90dd 100644
--- a/libvips/iofuncs/sink.c
+++ b/libvips/iofuncs/sink.c
@@ -211,6 +211,8 @@ vips_sink_base_init( SinkBase *sink_base, VipsImage *image )
 	vips_get_tile_size( image, 
 		&sink_base->tile_width, &sink_base->tile_height, 
 		&sink_base->nlines );
+
+	sink_base->processed = 0;
 }
 
 static int
@@ -283,6 +285,10 @@ vips_sink_base_allocate( VipsThreadState *state, void *a, gboolean *stop )
 	 */
 	sink_base->x += sink_base->tile_width;
 
+	/* Add the number of pixels we've just allocated to progress.
+	 */
+	sink_base->processed += state->pos.width * state->pos.height;
+
 	return( 0 );
 }
 
@@ -305,14 +311,12 @@ vips_sink_base_progress( void *a )
 {
 	SinkBase *sink_base = (SinkBase *) a;
 
-	VIPS_DEBUG_MSG( "vips_sink_base_progress: %d x %d\n",
-		sink_base->tile_width, sink_base->tile_height );
+	VIPS_DEBUG_MSG( "vips_sink_base_progress:\n" ); 
 
 	/* Trigger any eval callbacks on our source image and
 	 * check for errors.
 	 */
-	vips_image_eval( sink_base->im, 
-		sink_base->tile_width, sink_base->tile_height );
+	vips_image_eval( sink_base->im, sink_base->processed );
 	if( vips_image_get_kill( sink_base->im ) )
 		return( -1 );
 
diff --git a/libvips/iofuncs/sink.h b/libvips/iofuncs/sink.h
index e520fc0c..38843506 100644
--- a/libvips/iofuncs/sink.h
+++ b/libvips/iofuncs/sink.h
@@ -56,6 +56,10 @@ typedef struct _SinkBase {
 	int tile_height;
 	int nlines;
 
+	/* The number of pixels allocate has allocated. Used for progress
+	 * feedback.
+	 */
+	guint64 processed;
 } SinkBase;
 
 /* Some function we can share.
diff --git a/libvips/iofuncs/sinkdisc.c b/libvips/iofuncs/sinkdisc.c
index 432a0992..a8bda0b7 100644
--- a/libvips/iofuncs/sinkdisc.c
+++ b/libvips/iofuncs/sinkdisc.c
@@ -396,6 +396,10 @@ wbuffer_allocate_fn( VipsThreadState *state, void *a, gboolean *stop )
 	 */
 	sink_base->x += sink_base->tile_width;
 
+	/* Add the number of pixels we've just allocated to progress.
+	 */
+	sink_base->processed += state->pos.width * state->pos.height;
+
 	return( 0 );
 }
 
diff --git a/libvips/iofuncs/sinkmemory.c b/libvips/iofuncs/sinkmemory.c
index 375d5916..3b55d690 100644
--- a/libvips/iofuncs/sinkmemory.c
+++ b/libvips/iofuncs/sinkmemory.c
@@ -240,6 +240,10 @@ sink_memory_area_allocate_fn( VipsThreadState *state, void *a, gboolean *stop )
 	 */
 	sink_base->x += sink_base->tile_width;
 
+	/* Add the number of pixels we've just allocated to progress.
+	 */
+	sink_base->processed += state->pos.width * state->pos.height;
+
 	return( 0 );
 }