diff --git a/OpenRA.Mods.Common/Widgets/PerfGraphWidget.cs b/OpenRA.Mods.Common/Widgets/PerfGraphWidget.cs
index c04df9e4e9..4684b61f30 100644
--- a/OpenRA.Mods.Common/Widgets/PerfGraphWidget.cs
+++ b/OpenRA.Mods.Common/Widgets/PerfGraphWidget.cs
@@ -23,12 +23,16 @@ namespace OpenRA.Mods.Common.Widgets
 	{
 		readonly int dotWidth;
 		readonly int nextDotAdvance;
-		readonly Cache<string, int> textWidthCache;
-		readonly SpriteFont font = Game.Renderer.Fonts["Tiny"];
+		readonly Cache<string, int> textWidthCache = null;
+		readonly SpriteFont font = Game.Renderer?.Fonts["Tiny"];
 		StringBuilder builder = null;
 
 		public PerfGraphWidget()
 		{
+			// Skip if running format unit test
+			if (font == null)
+				return;
+
 			textWidthCache = new(GetTextWidth);
 			dotWidth = textWidthCache["."];
 			nextDotAdvance = textWidthCache[".."] - dotWidth;
@@ -51,8 +55,15 @@ namespace OpenRA.Mods.Common.Widgets
 				return;
 			}
 
-			value += 0.000005; // Do normal rounding instead of floor/trucate;
 			var intValue = (int)value;
+
+			// Do normal rounding instead of floor/trucate; account for numbers >= 100000 being 6 decimal places or "TooBig".
+			var frontPlaceMultipler = 1;
+			while (frontPlaceMultipler <= intValue && frontPlaceMultipler < 100000)
+				frontPlaceMultipler *= 10;
+			value += 0.000005 * frontPlaceMultipler;
+			intValue = (int)value;
+
 			if (intValue >= 1000000)
 			{
 				output.Append("TooBig");
diff --git a/OpenRA.Test/OpenRA.Mods.Common/PerfGraphWidgetTest.cs b/OpenRA.Test/OpenRA.Mods.Common/PerfGraphWidgetTest.cs
new file mode 100644
index 0000000000..26352992c3
--- /dev/null
+++ b/OpenRA.Test/OpenRA.Mods.Common/PerfGraphWidgetTest.cs
@@ -0,0 +1,103 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Text;
+using NUnit.Framework;
+using OpenRA.Mods.Common.Widgets;
+
+namespace OpenRA.Test
+{
+	[TestFixture]
+	sealed class PerfGraphWidgetTest
+	{
+		readonly PerfGraphWidget widget = new();
+		readonly StringBuilder output = new(6);
+
+		void AssertThat(double input, string expected)
+		{
+			output.Clear();
+			widget.SixCharacterFormatFloat(output, input);
+			Assert.That(output.ToString(), Is.EqualTo(expected));
+		}
+
+		[TestCase(TestName = "NaN is reported with 3 padding spaces after.")]
+		public void NaN()
+		{
+			AssertThat(double.NaN, "NaN   ");
+		}
+
+		[TestCase(TestName = "Negative numbers are discarded as \"<0\" with 4 padding spaces after.")]
+		public void Negative()
+		{
+			AssertThat(-0.000001, "<0    ");
+		}
+
+		[TestCase(TestName = "Numbers < 1 start with a decimal point ('.') and show 5 decimal places after the decimal point.")]
+		public void Fractional()
+		{
+			AssertThat(0, ".00000");
+			AssertThat(0.000001, ".00000");
+			AssertThat(0.000004, ".00000");
+			AssertThat(0.0000049, ".00000");
+			AssertThat(0.000005, ".00001");
+			AssertThat(0.000009, ".00001");
+			AssertThat(0.00001, ".00001");
+			AssertThat(0.00004, ".00004");
+			AssertThat(0.00005, ".00005");
+			AssertThat(0.00009, ".00009");
+			AssertThat(0.0001, ".00010");
+			AssertThat(0.0004, ".00040");
+			AssertThat(0.0005, ".00050");
+			AssertThat(0.0009, ".00090");
+			AssertThat(0.001, ".00100");
+			AssertThat(0.005, ".00500");
+			AssertThat(0.01, ".01000");
+			AssertThat(0.05, ".05000");
+			AssertThat(0.1, ".10000");
+			AssertThat(0.5, ".50000");
+		}
+
+		[TestCase(TestName = "Numbers >= 1 and < 100000 show the 5 most signifcant digits with a decimal point ('.').")]
+		public void FiveSignificantDigits()
+		{
+			AssertThat(1, "1.0000");
+			AssertThat(9, "9.0000");
+			AssertThat(9.00005, "9.0001");
+			AssertThat(10, "10.000");
+			AssertThat(99, "99.000");
+			AssertThat(99.0005, "99.001");
+			AssertThat(100, "100.00");
+			AssertThat(123.4321, "123.43");
+			AssertThat(999.005, "999.01");
+			AssertThat(1000, "1000.0");
+			AssertThat(9999.04999999, "9999.0");
+			AssertThat(9999.05000001, "9999.1"); // Binary conversion causes 9999.05 + 0.05 => 9999.099999999999.
+			AssertThat(10000, "10000.");
+		}
+
+		[TestCase(TestName = "Numbers >= 100000 and < 1000000 show the 5 most signifcant digits with a decimal point ('.').")]
+		public void SixSignificantDigits()
+		{
+			AssertThat(99999.9, "100000");
+			AssertThat(100000, "100000");
+			AssertThat(999999, "999999");
+		}
+
+		[TestCase(TestName = "Numbers >= 1000000 are very unlikely for perf measurements and would require different formatting.")]
+		public void TooBig()
+		{
+			AssertThat(1000000, "TooBig");
+			AssertThat(1234321, "TooBig");
+			AssertThat(10000000, "TooBig");
+			AssertThat(100000000, "TooBig");
+		}
+	}
+}