diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index 7cbd3e4a..fb49d46c 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -249,6 +249,20 @@ static struct wlr_output_impl output_impl = {
 	.destroy = wlr_drm_output_destroy,
 };
 
+static uint32_t calculate_refresh_rate(drmModeModeInfo *mode) {
+	uint32_t refresh = (mode->clock * 1000000LL / mode->htotal +
+		mode->vtotal / 2) / mode->vtotal;
+
+	if (mode->flags & DRM_MODE_FLAG_INTERLACE)
+		refresh *= 2;
+	if (mode->flags & DRM_MODE_FLAG_DBLSCAN)
+		refresh /= 2;
+	if (mode->vscan > 1)
+		refresh /= mode->vscan;
+
+	return refresh;
+}
+
 void wlr_drm_scan_connectors(struct wlr_backend_state *state) {
 	wlr_log(L_INFO, "Scanning DRM connectors");
 
@@ -321,14 +335,12 @@ void wlr_drm_scan_connectors(struct wlr_backend_state *state) {
 				struct wlr_output_mode *mode = calloc(1,
 						sizeof(struct wlr_output_mode));
 				mode->width = _state->mode.hdisplay;
-				// TODO: Calculate more accurate refresh rate
-				// TODO: Check that this refresh rate is mHz
 				mode->height = _state->mode.vdisplay;
+				mode->refresh = calculate_refresh_rate(&_state->mode);
 				mode->state = _state;
 
-				wlr_log(L_INFO, "  %"PRIu16"@%"PRIu16"@%"PRIu32,
-					_state->mode.hdisplay, _state->mode.vdisplay,
-					_state->mode.vrefresh);
+				wlr_log(L_INFO, "  %"PRIu32"@%"PRIu32"@%"PRIu32,
+					mode->width, mode->height, mode->refresh);
 
 				list_add(wlr_output->modes, mode);
 			}
diff --git a/include/wlr/wayland.h b/include/wlr/wayland.h
index 158acc33..de3f5f10 100644
--- a/include/wlr/wayland.h
+++ b/include/wlr/wayland.h
@@ -10,8 +10,8 @@ struct wlr_output_mode_state;
 struct wlr_output_mode {
 	struct wlr_output_mode_state *state;
 	uint32_t flags; // enum wl_output_mode
-	int32_t width, height;
-	int32_t refresh; // mHz
+	uint32_t width, height;
+	uint32_t refresh; // mHz
 };
 
 struct wlr_output_impl;