diff --git a/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/FormattingHelpers.CountDigits.cs b/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/FormattingHelpers.CountDigits.cs
index 22eff2b8b16834..cb9f5369c0315b 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/FormattingHelpers.CountDigits.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/FormattingHelpers.CountDigits.cs
@@ -1,9 +1,11 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Buffers.Binary;
 using System.Diagnostics;
 using System.Numerics;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 namespace System.Buffers.Text
 {
@@ -109,36 +111,52 @@ public static int CountDigits(ulong value)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static int CountDigits(uint value)
         {
-            int digits = 1;
-            if (value >= 100000)
-            {
-                value /= 100000;
-                digits += 5;
-            }
-
-            if (value < 10)
-            {
-                // no-op
-            }
-            else if (value < 100)
-            {
-                digits++;
-            }
-            else if (value < 1000)
-            {
-                digits += 2;
-            }
-            else if (value < 10000)
-            {
-                digits += 3;
-            }
-            else
-            {
-                Debug.Assert(value < 100000);
-                digits += 4;
-            }
-
-            return digits;
+            // Algorithm based on https://lemire.me/blog/2021/06/03/computing-the-number-of-digits-of-an-integer-even-faster.
+            // TODO https://github.com/dotnet/runtime/issues/60948: Use ReadOnlySpan<long> instead of ReadOnlySpan<byte>.
+            ReadOnlySpan<byte> table = new byte[]
+            {
+                0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, // 4294967296
+                0xF6, 0xFF, 0xFF, 0xFF, 0x01, 0x00, 0x00, 0x00, // 8589934582
+                0xF6, 0xFF, 0xFF, 0xFF, 0x01, 0x00, 0x00, 0x00, // 8589934582
+                0xF6, 0xFF, 0xFF, 0xFF, 0x01, 0x00, 0x00, 0x00, // 8589934582
+                0x9C, 0xFF, 0xFF, 0xFF, 0x02, 0x00, 0x00, 0x00, // 12884901788
+                0x9C, 0xFF, 0xFF, 0xFF, 0x02, 0x00, 0x00, 0x00, // 12884901788
+                0x9C, 0xFF, 0xFF, 0xFF, 0x02, 0x00, 0x00, 0x00, // 12884901788
+                0x18, 0xFC, 0xFF, 0xFF, 0x03, 0x00, 0x00, 0x00, // 17179868184
+                0x18, 0xFC, 0xFF, 0xFF, 0x03, 0x00, 0x00, 0x00, // 17179868184
+                0x18, 0xFC, 0xFF, 0xFF, 0x03, 0x00, 0x00, 0x00, // 17179868184
+                0xF0, 0xD8, 0xFF, 0xFF, 0x04, 0x00, 0x00, 0x00, // 21474826480
+                0xF0, 0xD8, 0xFF, 0xFF, 0x04, 0x00, 0x00, 0x00, // 21474826480
+                0xF0, 0xD8, 0xFF, 0xFF, 0x04, 0x00, 0x00, 0x00, // 21474826480
+                0xF0, 0xD8, 0xFF, 0xFF, 0x04, 0x00, 0x00, 0x00, // 21474826480
+                0x60, 0x79, 0xFE, 0xFF, 0x05, 0x00, 0x00, 0x00, // 25769703776
+                0x60, 0x79, 0xFE, 0xFF, 0x05, 0x00, 0x00, 0x00, // 25769703776
+                0x60, 0x79, 0xFE, 0xFF, 0x05, 0x00, 0x00, 0x00, // 25769703776
+                0xC0, 0xBD, 0xF0, 0xFF, 0x06, 0x00, 0x00, 0x00, // 30063771072
+                0xC0, 0xBD, 0xF0, 0xFF, 0x06, 0x00, 0x00, 0x00, // 30063771072
+                0xC0, 0xBD, 0xF0, 0xFF, 0x06, 0x00, 0x00, 0x00, // 30063771072
+                0x80, 0x69, 0x67, 0xFF, 0x07, 0x00, 0x00, 0x00, // 34349738368
+                0x80, 0x69, 0x67, 0xFF, 0x07, 0x00, 0x00, 0x00, // 34349738368
+                0x80, 0x69, 0x67, 0xFF, 0x07, 0x00, 0x00, 0x00, // 34349738368
+                0x80, 0x69, 0x67, 0xFF, 0x07, 0x00, 0x00, 0x00, // 34349738368
+                0x00, 0x1F, 0x0A, 0xFA, 0x08, 0x00, 0x00, 0x00, // 38554705664
+                0x00, 0x1F, 0x0A, 0xFA, 0x08, 0x00, 0x00, 0x00, // 38554705664
+                0x00, 0x1F, 0x0A, 0xFA, 0x08, 0x00, 0x00, 0x00, // 38554705664
+                0x00, 0x36, 0x65, 0xC4, 0x09, 0x00, 0x00, 0x00, // 41949672960
+                0x00, 0x36, 0x65, 0xC4, 0x09, 0x00, 0x00, 0x00, // 41949672960
+                0x00, 0x36, 0x65, 0xC4, 0x09, 0x00, 0x00, 0x00, // 41949672960
+                0x00, 0x00, 0x00, 0x00, 0x0A, 0x00, 0x00, 0x00, // 42949672960
+                0x00, 0x00, 0x00, 0x00, 0x0A, 0x00, 0x00, 0x00, // 42949672960
+            };
+            Debug.Assert(table.Length == (32 * sizeof(long)), "Every result of uint.Log2(value) needs a long entry in the table.");
+
+            long tableValue = Unsafe.ReadUnaligned<long>(ref Unsafe.Add(ref MemoryMarshal.GetReference(table), uint.Log2(value) * sizeof(long)));
+            if (!BitConverter.IsLittleEndian)
+            {
+                tableValue = BinaryPrimitives.ReverseEndianness(tableValue);
+            }
+
+            return (int)((value + tableValue) >> 32);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
diff --git a/src/libraries/System.Private.CoreLib/src/System/Number.Formatting.cs b/src/libraries/System.Private.CoreLib/src/System/Number.Formatting.cs
index 9268f341d7dac5..2faf5707a7f7bb 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Number.Formatting.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Number.Formatting.cs
@@ -1593,15 +1593,14 @@ private static unsafe void UInt32ToNumber(uint value, ref NumberBuffer number)
 
         internal static unsafe string UInt32ToDecStr(uint value)
         {
-            // Intrinsified in mono interpreter
-            int bufferLength = FormattingHelpers.CountDigits(value);
-
             // For single-digit values that are very common, especially 0 and 1, just return cached strings.
-            if (bufferLength == 1)
+            if (value < 10)
             {
                 return s_singleDigitStringCache[value];
             }
 
+            int bufferLength = FormattingHelpers.CountDigits(value);
+
             string result = string.FastAllocateString(bufferLength);
             fixed (char* buffer = result)
             {
@@ -1935,15 +1934,14 @@ private static uint Int64DivMod1E9(ref ulong value)
 
         internal static unsafe string UInt64ToDecStr(ulong value)
         {
-            // Intrinsified in mono interpreter
-            int bufferLength = FormattingHelpers.CountDigits(value);
-
             // For single-digit values that are very common, especially 0 and 1, just return cached strings.
-            if (bufferLength == 1)
+            if (value < 10)
             {
                 return s_singleDigitStringCache[value];
             }
 
+            int bufferLength = FormattingHelpers.CountDigits(value);
+
             string result = string.FastAllocateString(bufferLength);
             fixed (char* buffer = result)
             {