diff --git a/cue/src/app.rs b/cue/src/app.rs
index 4a5ffba..643372b 100644
--- a/cue/src/app.rs
+++ b/cue/src/app.rs
@@ -98,6 +98,8 @@ pub enum Message {
     CalBleachChanged(String),
     CalTempChanged(String),
     CalComputeK,
+    ClCalKnownPpmChanged(String),
+    ClSetFactor,
     /* Global */
     PollTemp,
     NativeMenuTick,
@@ -227,6 +229,8 @@ pub struct App {
     cal_bleach_pct: String,
     cal_temp_c: String,
     cal_cell_constant: Option<f32>,
+    cl_factor: Option<f32>,
+    cl_cal_known_ppm: String,
 
     /* Global */
     temp_c: f32,
@@ -457,6 +461,8 @@ impl App {
             cal_bleach_pct: "7.825".into(),
             cal_temp_c: "40".into(),
             cal_cell_constant: None,
+            cl_factor: None,
+            cl_cal_known_ppm: String::from("5"),
 
             temp_c: 25.0,
             conn_gen: 0,
@@ -561,6 +567,7 @@ impl App {
                 self.connected = true;
                 self.send_cmd(&protocol::build_sysex_get_config());
                 self.send_cmd(&protocol::build_sysex_get_cell_k());
+                self.send_cmd(&protocol::build_sysex_get_cl_factor());
             }
             Message::DeviceStatus(s) => {
                 if s.contains("Reconnecting") || s.contains("Connecting") {
@@ -734,6 +741,10 @@ impl App {
                     self.cal_cell_constant = Some(k);
                     self.status = format!("Device cell constant: {:.4} cm-1", k);
                 }
+                EisMessage::ClFactor(f) => {
+                    self.cl_factor = Some(f);
+                    self.status = format!("Device Cl factor: {:.6}", f);
+                }
             },
             Message::TabSelected(t) => {
                 if t == Tab::Browse {
@@ -951,6 +962,19 @@ impl App {
                     self.status = "No valid EIS data for Rs extraction".into();
                 }
             }
+            Message::ClCalKnownPpmChanged(s) => { self.cl_cal_known_ppm = s; }
+            Message::ClSetFactor => {
+                let known_ppm = self.cl_cal_known_ppm.parse::<f32>().unwrap_or(0.0);
+                if let Some(r) = &self.cl_result {
+                    let peak = r.i_free_ua.abs();
+                    if peak > 0.0 {
+                        let factor = known_ppm / peak;
+                        self.cl_factor = Some(factor);
+                        self.send_cmd(&protocol::build_sysex_set_cl_factor(factor));
+                        self.status = format!("Cl factor: {:.6} ppm/uA", factor);
+                    }
+                }
+            }
             /* Clean */
             Message::CleanVChanged(s) => self.clean_v = s,
             Message::CleanDurChanged(s) => self.clean_dur = s,
@@ -1538,6 +1562,10 @@ impl App {
                         "Free: {:.3} uA | Total: {:.3} uA | Combined: {:.3} uA",
                         r.i_free_ua, r.i_total_ua, r.i_total_ua - r.i_free_ua
                     ));
+                    if let (Some(f), Some(r)) = (self.cl_factor, &self.cl_result) {
+                        let ppm = f * r.i_free_ua.abs();
+                        result_parts.push(format!("Free Cl: {:.2} ppm", ppm));
+                    }
                     if let Some((_, ref_r)) = &self.cl_ref {
                         let df = r.i_free_ua - ref_r.i_free_ua;
                         let dt = r.i_total_ua - ref_r.i_total_ua;
@@ -1645,6 +1673,28 @@ impl App {
             .on_press(Message::CalComputeK);
         results = results.push(compute_btn);
 
+        results = results.push(iced::widget::horizontal_rule(1));
+        results = results.push(text("Chlorine Calibration").size(16));
+        if let Some(f) = self.cl_factor {
+            results = results.push(text(format!("Cl factor: {:.6} ppm/uA", f)).size(14));
+        }
+        if let Some(r) = &self.cl_result {
+            results = results.push(text(format!("Last free Cl peak: {:.3} uA", r.i_free_ua)).size(14));
+        }
+        results = results.push(
+            row![
+                column![
+                    text("Known Cl ppm").size(12),
+                    text_input("5", &self.cl_cal_known_ppm)
+                        .on_input(Message::ClCalKnownPpmChanged).width(80),
+                ].spacing(2),
+                button(text("Set Cl Factor").size(13))
+                    .style(style_action())
+                    .padding([6, 16])
+                    .on_press(Message::ClSetFactor),
+            ].spacing(10).align_y(iced::Alignment::End)
+        );
+
         row![
             container(inputs).width(Length::FillPortion(2)),
             iced::widget::vertical_rule(1),