diff --git a/profile.c b/profile.c
index 6efd05eb7..521e6f68f 100644
--- a/profile.c
+++ b/profile.c
@@ -597,6 +597,7 @@ struct plot_data *populate_plot_entries(struct dive *dive, struct divecomputer *
 		entry->sec = time;
 		entry->depth = depth;
 
+		entry->running_sum = (entry - 1)->running_sum + (time - lasttime) * (depth + lastdepth) / 2;
 		entry->stopdepth = sample->stopdepth.mm;
 		entry->stoptime = sample->stoptime.seconds;
 		entry->ndl = sample->ndl.seconds;
diff --git a/profile.h b/profile.h
index 5d2009530..5c30ca4de 100644
--- a/profile.h
+++ b/profile.h
@@ -39,6 +39,7 @@ struct plot_data {
 	int cns;
 	int smoothed;
 	int sac;
+	int running_sum;
 	struct gas_pressures pressures;
 	pressure_t o2pressure;  // for rebreathers, this is consensus measured po2, or setpoint otherwise. 0 for OC.
 	pressure_t o2sensor[3]; //for rebreathers with up to 3 PO2 sensors