diff --git a/komorebi-core/src/arrangement.rs b/komorebi-core/src/arrangement.rs
index eb23a726..657267c2 100644
--- a/komorebi-core/src/arrangement.rs
+++ b/komorebi-core/src/arrangement.rs
@@ -256,15 +256,44 @@ impl Arrangement for CustomLayout {
                 Option::from(1)
             };
 
+            #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
+            let primary_right = self.primary_width_percentage().map_or_else(
+                || area.right / self.len() as i32,
+                |percentage| (area.right / 100) * percentage as i32,
+            );
+
             for (idx, column) in self.iter().enumerate() {
                 // If we are offsetting a tertiary column for which the threshold
                 // has not yet been met, this loop should not run for that final
                 // tertiary column
                 if idx < self.len() - offset.unwrap_or(0) {
-                    let column_area = self.column_area(area, idx, offset);
+                    let column_area = if idx == 0 {
+                        Self::column_area_with_last(self.len(), area, primary_right, None, offset)
+                    } else {
+                        Self::column_area_with_last(
+                            self.len(),
+                            area,
+                            primary_right,
+                            Option::from(dimensions[self.first_container_idx(idx - 1)]),
+                            offset,
+                        )
+                    };
 
                     match column {
-                        Column::Primary | Column::Secondary(None) => {
+                        Column::Primary(Option::Some(_)) => {
+                            let main_column_area = if idx == 0 {
+                                Self::main_column_area(area, primary_right, None)
+                            } else {
+                                Self::main_column_area(
+                                    area,
+                                    primary_right,
+                                    Option::from(dimensions[self.first_container_idx(idx - 1)]),
+                                )
+                            };
+
+                            dimensions.push(main_column_area);
+                        }
+                        Column::Primary(None) | Column::Secondary(None) => {
                             dimensions.push(column_area);
                         }
                         Column::Secondary(Some(split)) => match split {
@@ -278,6 +307,14 @@ impl Arrangement for CustomLayout {
                             }
                         },
                         Column::Tertiary(split) => {
+                            let column_area = Self::column_area_with_last(
+                                self.len(),
+                                area,
+                                primary_right,
+                                Option::from(dimensions[self.first_container_idx(idx - 1)]),
+                                offset,
+                            );
+
                             let remaining = container_count - tertiary_trigger_threshold;
 
                             match split {
diff --git a/komorebi-core/src/custom_layout.rs b/komorebi-core/src/custom_layout.rs
index b8aa457a..79ad64d6 100644
--- a/komorebi-core/src/custom_layout.rs
+++ b/komorebi-core/src/custom_layout.rs
@@ -28,7 +28,7 @@ impl CustomLayout {
     #[must_use]
     pub fn primary_idx(&self) -> Option<usize> {
         for (i, column) in self.iter().enumerate() {
-            if let Column::Primary = column {
+            if let Column::Primary(_) = column {
                 return Option::from(i);
             }
         }
@@ -36,6 +36,18 @@ impl CustomLayout {
         None
     }
 
+    #[must_use]
+    pub fn primary_width_percentage(&self) -> Option<usize> {
+        for column in self.iter() {
+            if let Column::Primary(Option::Some(ColumnWidth::WidthPercentage(percentage))) = column
+            {
+                return Option::from(*percentage);
+            }
+        }
+
+        None
+    }
+
     #[must_use]
     pub fn is_valid(&self) -> bool {
         // A valid layout must have at least one column
@@ -63,7 +75,7 @@ impl CustomLayout {
 
         for column in self.iter() {
             match column {
-                Column::Primary => primaries += 1,
+                Column::Primary(_) => primaries += 1,
                 Column::Tertiary(_) => tertiaries += 1,
                 Column::Secondary(_) => {}
             }
@@ -78,7 +90,7 @@ impl CustomLayout {
 
         for (idx, column) in self.iter().enumerate() {
             match column {
-                Column::Primary | Column::Secondary(None) => {
+                Column::Primary(_) | Column::Secondary(None) => {
                     count_map.insert(idx, 1);
                 }
                 Column::Secondary(Some(split)) => {
@@ -156,16 +168,60 @@ impl CustomLayout {
             bottom: work_area.bottom,
         }
     }
+
+    #[must_use]
+    pub fn column_area_with_last(
+        len: usize,
+        work_area: &Rect,
+        primary_right: i32,
+        last_column: Option<Rect>,
+        offset: Option<usize>,
+    ) -> Rect {
+        let divisor = offset.map_or_else(|| len - 1, |offset| len - offset - 1);
+
+        #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+        let equal_width = (work_area.right - primary_right) / divisor as i32;
+        let left = last_column.map_or(work_area.left, |last| last.left + last.right);
+        let right = equal_width;
+
+        Rect {
+            left,
+            top: work_area.top,
+            right,
+            bottom: work_area.bottom,
+        }
+    }
+
+    #[must_use]
+    pub fn main_column_area(
+        work_area: &Rect,
+        primary_right: i32,
+        last_column: Option<Rect>,
+    ) -> Rect {
+        let left = last_column.map_or(work_area.left, |last| last.left + last.right);
+
+        Rect {
+            left,
+            top: work_area.top,
+            right: primary_right,
+            bottom: work_area.bottom,
+        }
+    }
 }
 
 #[derive(Clone, Copy, Debug, Serialize, Deserialize)]
 #[serde(tag = "column", content = "configuration")]
 pub enum Column {
-    Primary,
+    Primary(Option<ColumnWidth>),
     Secondary(Option<ColumnSplitWithCapacity>),
     Tertiary(ColumnSplit),
 }
 
+#[derive(Clone, Copy, Debug, Serialize, Deserialize)]
+pub enum ColumnWidth {
+    WidthPercentage(usize),
+}
+
 #[derive(Clone, Copy, Debug, Serialize, Deserialize)]
 pub enum ColumnSplit {
     Horizontal,
diff --git a/komorebi/src/window_manager.rs b/komorebi/src/window_manager.rs
index b5c79e9a..ab1864d4 100644
--- a/komorebi/src/window_manager.rs
+++ b/komorebi/src/window_manager.rs
@@ -1040,9 +1040,10 @@ impl WindowManager {
         match workspace.layout() {
             Layout::Default(_) => {}
             Layout::Custom(layout) => {
-                let primary_idx = layout
-                    .primary_idx()
-                    .ok_or_else(|| anyhow!("this custom layout does not have a primary column"))?;
+                let primary_idx =
+                    layout.first_container_idx(layout.primary_idx().ok_or_else(|| {
+                        anyhow!("this custom layout does not have a primary column")
+                    })?);
 
                 if !workspace.containers().is_empty() && primary_idx < workspace.containers().len()
                 {
@@ -1067,9 +1068,10 @@ impl WindowManager {
 
         match workspace.layout() {
             Layout::Default(_) => {
-                let primary_idx = layout
-                    .primary_idx()
-                    .ok_or_else(|| anyhow!("this custom layout does not have a primary column"))?;
+                let primary_idx =
+                    layout.first_container_idx(layout.primary_idx().ok_or_else(|| {
+                        anyhow!("this custom layout does not have a primary column")
+                    })?);
 
                 if !workspace.containers().is_empty() && primary_idx < workspace.containers().len()
                 {
diff --git a/komorebi/src/workspace.rs b/komorebi/src/workspace.rs
index b6a357ce..b841e3ce 100644
--- a/komorebi/src/workspace.rs
+++ b/komorebi/src/workspace.rs
@@ -352,15 +352,17 @@ impl Workspace {
 
         let primary_idx = match self.layout() {
             Layout::Default(_) => 0,
-            Layout::Custom(layout) => layout
-                .primary_idx()
-                .ok_or_else(|| anyhow!("this custom layout does not have a primary column"))?,
+            Layout::Custom(layout) => layout.first_container_idx(
+                layout
+                    .primary_idx()
+                    .ok_or_else(|| anyhow!("this custom layout does not have a primary column"))?,
+            ),
         };
 
         self.containers_mut().insert(primary_idx, container);
         self.resize_dimensions_mut().insert(primary_idx, resize);
 
-        self.focus_container(0);
+        self.focus_container(primary_idx);
 
         Ok(())
     }