diff --git a/crates/ui/src/plot/scale/point.rs b/crates/ui/src/plot/scale/point.rs
index 49ff821c..74f45e95 100644
--- a/crates/ui/src/plot/scale/point.rs
+++ b/crates/ui/src/plot/scale/point.rs
@@ -9,6 +9,7 @@ use super::Scale;
 pub struct ScalePoint<T> {
     domain: Vec<T>,
     range_tick: f32,
+    least_index_range_tick: f32,
 }
 
 impl<T> ScalePoint<T>
@@ -17,8 +18,8 @@ where
 {
     pub fn new(domain: Vec<T>, range: Vec<f32>) -> Self {
         let len = domain.len();
-        let range_tick = if len.is_zero() {
-            0.
+        let (range_tick, least_index_range_tick) = if len.is_zero() {
+            (0., 0.)
         } else {
             let range_diff = range
                 .iter()
@@ -26,10 +27,14 @@ where
                 .into_option()
                 .map_or(0., |(min, max)| max - min);
 
-            range_diff / (len as f32)
+            (range_diff / (len - 1) as f32, range_diff / len as f32)
         };
 
-        Self { domain, range_tick }
+        Self {
+            domain,
+            range_tick,
+            least_index_range_tick,
+        }
     }
 }
 
@@ -47,7 +52,7 @@ where
             return 0;
         }
 
-        let index = (tick / self.range_tick).round() as usize;
+        let index = (tick / self.least_index_range_tick).round() as usize;
         index.min(self.domain.len().saturating_sub(1))
     }
 }