diff --git a/draftlogs/7581_fix.md b/draftlogs/7581_fix.md
new file mode 100644
index 00000000000..c3f1a5950dc
--- /dev/null
+++ b/draftlogs/7581_fix.md
@@ -0,0 +1 @@
+- Fix KDE sampling precision in violin trace to eliminate floating-point drift and prevent density underrun/overrun ([#7581](https://github.com/plotly/plotly.js/pull/7581))
diff --git a/src/traces/violin/calc.js b/src/traces/violin/calc.js
index 39fa549097b..4baad80e0d0 100644
--- a/src/traces/violin/calc.js
+++ b/src/traces/violin/calc.js
@@ -48,9 +48,11 @@ module.exports = function calc(gd, trace) {
             }
 
             var kde = helpers.makeKDE(cdi, trace, vals);
-            cdi.density = new Array(n);
+            // n intervals means n + 1 sample points to include both endpoints
+            cdi.density = new Array(n + 1);
 
-            for(var k = 0, t = span[0]; t < (span[1] + step / 2); k++, t += step) {
+            for(var k = 0; k <= n; k++) {
+                var t = span[0] + k * step;
                 var v = kde(t);
                 cdi.density[k] = {v: v, t: t};
                 maxKDE = Math.max(maxKDE, v);
diff --git a/test/image/baselines/violin_box_overlay.png b/test/image/baselines/violin_box_overlay.png
index 7150d01fb0b..d03af33ebb6 100644
Binary files a/test/image/baselines/violin_box_overlay.png and b/test/image/baselines/violin_box_overlay.png differ
diff --git a/test/jasmine/tests/violin_test.js b/test/jasmine/tests/violin_test.js
index c96a8dedd06..375aa92aa39 100644
--- a/test/jasmine/tests/violin_test.js
+++ b/test/jasmine/tests/violin_test.js
@@ -401,6 +401,20 @@ describe('Test violin calc:', function() {
         expect(cd.length).toBe(1, '# of violins');
         expect(cd[0].bandwidth).toBe(0, 'bandwidth');
     });
+
+    it('should produce exactly n + 1 density samples for tiny or near-equal spans', function() {
+        var cd = _calc({
+            type: 'violin',
+            x: [0, 0],
+            y: [0.5006312999999999, 0.5006313]
+        });
+        var cdi = cd[0];
+
+        var dist = cdi.span[1] - cdi.span[0];
+        var n = Math.ceil(dist / (cdi.bandwidth / 3));
+
+        expect(cdi.density.length).toBe(n + 1);
+    });
 });
 
 describe('Test violin hover:', function() {