diff --git a/core/plannernotes.cpp b/core/plannernotes.cpp
index 4cea0a792..7c39b2578 100644
--- a/core/plannernotes.cpp
+++ b/core/plannernotes.cpp
@@ -443,7 +443,7 @@ void diveplan::add_plan_to_notes(struct dive &dive, bool show_disclaimer, planne
 
 	{
 		const char *depth_unit;
-		int altitude = (int) get_depth_units((int) (pressure_to_altitude(surface_pressure)), NULL, &depth_unit);
+		int altitude = (int) get_depth_units(pressure_to_altitude(surface_pressure).mm, NULL, &depth_unit);
 
 		buf += casprintf_loc(translate("gettextFromC", "ATM pressure: %dmbar (%d%s)<br/>\n</div>\n"), surface_pressure, altitude, depth_unit);
 	}
diff --git a/core/units.cpp b/core/units.cpp
index 7d855840e..c32810e2e 100644
--- a/core/units.cpp
+++ b/core/units.cpp
@@ -204,3 +204,8 @@ depth_t m_or_ft(int m, int ft)
 	int mm = prefs.units.length == units::METERS ? m * 1000 : feet_to_mm(ft);
 	return depth_t::from_base(mm);
 }
+
+depth_t pressure_to_altitude(pressure_t pressure)
+{						// returns altitude in mm above sea level
+	return depth_t::from_base(static_cast<int32_t>(log(1013.0 / pressure.mbar) * 7800000));
+}
diff --git a/core/units.h b/core/units.h
index 5e6718084..79ad9ac98 100644
--- a/core/units.h
+++ b/core/units.h
@@ -436,10 +436,7 @@ static inline pressure_t altitude_to_pressure(int32_t altitude) { 	// altitude i
 	return pressure_t { .mbar = int_cast<int32_t> (1013.0 * exp(- altitude / 7800000.0)) };
 }
 
-static inline int32_t pressure_to_altitude(pressure_t pressure)
-{						// returns altitude in mm above sea level
-	return (int32_t) (log(1013.0 / pressure.mbar) * 7800000);
-}
+depth_t pressure_to_altitude(pressure_t pressure);
 
 /*
  * We keep our internal data in well-specified units, but
diff --git a/desktop-widgets/diveplanner.cpp b/desktop-widgets/diveplanner.cpp
index 2184f6fce..5015fd542 100644
--- a/desktop-widgets/diveplanner.cpp
+++ b/desktop-widgets/diveplanner.cpp
@@ -163,7 +163,7 @@ void DivePlannerWidget::settingsChanged()
 	}
 	ui.tableWidget->view()->setItemDelegateForColumn(DivePlannerPointsModel::DEPTH, new SpinBoxDelegate(0, maxDepth, 1, this));
 	ui.atmHeight->blockSignals(true);
-	ui.atmHeight->setValue((int) get_depth_units((int) pressure_to_altitude(DivePlannerPointsModel::instance()->getSurfacePressure()), NULL, NULL));
+	ui.atmHeight->setValue((int) get_depth_units(pressure_to_altitude(DivePlannerPointsModel::instance()->getSurfacePressure()).mm, NULL, NULL));
 	ui.atmHeight->blockSignals(false);
 
 	ui.dateEdit->setDisplayFormat(QString::fromStdString(prefs.date_format));
@@ -175,7 +175,7 @@ void DivePlannerWidget::atmPressureChanged(int pressure_in_mbar)
 	pressure_t pressure { .mbar = pressure_in_mbar };
 	DivePlannerPointsModel::instance()->setSurfacePressure(pressure);
 	ui.atmHeight->blockSignals(true);
-	ui.atmHeight->setValue((int) get_depth_units((int) pressure_to_altitude(pressure), NULL, NULL));
+	ui.atmHeight->setValue((int) get_depth_units(pressure_to_altitude(pressure).mm, NULL, NULL));
 	ui.atmHeight->blockSignals(false);
 }
 
diff --git a/desktop-widgets/tab-widgets/TabDiveInformation.cpp b/desktop-widgets/tab-widgets/TabDiveInformation.cpp
index b4ce8576d..61e8e0baa 100644
--- a/desktop-widgets/tab-widgets/TabDiveInformation.cpp
+++ b/desktop-widgets/tab-widgets/TabDiveInformation.cpp
@@ -442,12 +442,12 @@ void TabDiveInformation::updateTextBox(int event) // Either the text box has bee
 			} else { // i.e. event == COMBO_CHANGED, that is, "m" or "ft" was selected from combobox
 				 // Show estimated altitude
 				bool ok;
-				double convertVal = 0.0010;	// Metric conversion fro mm to m
 				pressure_t pressure = { .mbar = ui->atmPressVal->text().toInt(&ok,10) };
 				if (ok && ui->atmPressVal->text().length()) {  // Show existing atm press as an altitude:
-					if (prefs.units.length == units::FEET) // For imperial units
-						convertVal = mm_to_feet(1);    // convert from mm to ft
-					ui->atmPressVal->setText(QString::number((int)(pressure_to_altitude(pressure) * convertVal)));
+					double convertVal = (prefs.units.length == units::FEET) ?
+						mm_to_feet(1) :		// convert from mm to ft
+						0.001;			// Metric conversion fro mm to m
+					ui->atmPressVal->setText(QString::number((int)(pressure_to_altitude(pressure).mm * convertVal)));
 				}
 			}
 			break;