diff --git a/src/coreclr/ToolBox/SOS/DacTableGen/diautil.cs b/src/coreclr/ToolBox/SOS/DacTableGen/diautil.cs
index 8da9217b477bc0..28af4119833668 100644
--- a/src/coreclr/ToolBox/SOS/DacTableGen/diautil.cs
+++ b/src/coreclr/ToolBox/SOS/DacTableGen/diautil.cs
@@ -619,7 +619,7 @@ private String GetTypeString(IDiaSymbol s)
         else if (tag == SymTagEnum.SymTagBaseType)
         {
             BasicType bt = (BasicType) s.baseType;
-            str.AppendFormat("(base type={0}, len={1:d})", bt.ToString(), s.length);
+            str.Append($"(base type={bt}, len={s.length:d})");
         }
         else if (tag == SymTagEnum.SymTagArrayType)
         {
@@ -677,7 +677,7 @@ private String GetTypeString(IDiaSymbol s)
                 try
                 {
                     succ = true;
-                    str.AppendFormat("[{0:d}]", s.length/s.type.length );
+                    str.Append($"[{s.length/s.type.length:d}]");
                 }
                 catch (Exception)
                 {
diff --git a/src/coreclr/tools/Common/TypeSystem/IL/ILDisassembler.cs b/src/coreclr/tools/Common/TypeSystem/IL/ILDisassembler.cs
index 2d1a626cc633d9..f11ed8cf5db8e1 100644
--- a/src/coreclr/tools/Common/TypeSystem/IL/ILDisassembler.cs
+++ b/src/coreclr/tools/Common/TypeSystem/IL/ILDisassembler.cs
@@ -227,8 +227,7 @@ private unsafe double ReadILDouble()
 
         public static void AppendOffset(StringBuilder sb, int offset)
         {
-            sb.Append("IL_");
-            sb.AppendFormat("{0:X4}", offset);
+            sb.Append($"IL_{offset:X4}");
         }
 
         private static void PadForInstructionArgument(StringBuilder sb)
diff --git a/src/coreclr/tools/r2rdump/CoreDisTools.cs b/src/coreclr/tools/r2rdump/CoreDisTools.cs
index 75029e04a163c9..8c917662014141 100644
--- a/src/coreclr/tools/r2rdump/CoreDisTools.cs
+++ b/src/coreclr/tools/r2rdump/CoreDisTools.cs
@@ -396,17 +396,17 @@ private void ProbeX64Quirks(RuntimeFunction rtf, int imageOffset, int rtfOffset,
                 {
                     if (targetName != null)
                     {
-                        translated.AppendFormat("[{0}]", targetName);
+                        translated.Append($"[{targetName}]");
                     }
                     else
                     {
-                        translated.AppendFormat("[0x{0:x4}]", target);
+                        translated.Append($"[0x{target:x4}]");
                     }
                     translated.Append(instruction, rightBracketPlusOne, instruction.Length - rightBracketPlusOne);
                 }
                 else
                 {
-                    translated.AppendFormat("[0x{0:x4}]", target);
+                    translated.Append($"[0x{target:x4}]");
                     translated.Append(instruction, rightBracketPlusOne, instruction.Length - rightBracketPlusOne);
                     if (targetName != null)
                     {
@@ -449,17 +449,17 @@ private void ProbeX86Quirks(RuntimeFunction rtf, int imageOffset, int rtfOffset,
                 {
                     if (targetName != null)
                     {
-                        translated.AppendFormat("[{0}]", targetName);
+                        translated.Append($"[{targetName}]");
                     }
                     else
                     {
-                        translated.AppendFormat("[0x{0:x4}]", target);
+                        translated.Append($"[0x{target:x4}]");
                     }
                     translated.Append(instruction, rightBracketPlusOne, instruction.Length - rightBracketPlusOne);
                 }
                 else
                 {
-                    translated.AppendFormat("[0x{0:x4}]", target);
+                    translated.Append($"[0x{target:x4}]");
                     translated.Append(instruction, rightBracketPlusOne, instruction.Length - rightBracketPlusOne);
                     if (targetName != null)
                     {
@@ -818,7 +818,7 @@ private void ProbeArm64Quirks(RuntimeFunction rtf, int imageOffset, int rtfOffse
                     }
                     else
                     {
-                        translated.AppendFormat("#0x{0:x4}", targetPage);
+                        translated.Append($"#0x{targetPage:x4}");
                     }
 
                     instruction = translated.ToString();
@@ -843,7 +843,7 @@ private void ProbeArm64Quirks(RuntimeFunction rtf, int imageOffset, int rtfOffse
                 }
                 else
                 {
-                    translated.AppendFormat("#0x{0:x}", target & 0xfff);
+                    translated.Append($"#0x{target & 0xfff:x}");
                     if (targetName != null)
                     {
                         AppendComment(translated, "import{" + targetName + "}");
diff --git a/src/coreclr/tools/r2rdump/R2RDiff.cs b/src/coreclr/tools/r2rdump/R2RDiff.cs
index 91962d3ee929af..9bea8d860f202d 100644
--- a/src/coreclr/tools/r2rdump/R2RDiff.cs
+++ b/src/coreclr/tools/r2rdump/R2RDiff.cs
@@ -281,7 +281,7 @@ private void ShowDiff(Dictionary<string, int> leftObjects, Dictionary<string, in
                 StringBuilder line = new StringBuilder();
                 if (inLeft)
                 {
-                    line.AppendFormat("{0,10}", leftSize);
+                    line.Append($"{leftSize,10}");
                 }
                 else
                 {
@@ -289,7 +289,7 @@ private void ShowDiff(Dictionary<string, int> leftObjects, Dictionary<string, in
                 }
                 if (inRight)
                 {
-                    line.AppendFormat("{0,11}", rightSize);
+                    line.Append($"{rightSize,11}");
                 }
                 else
                 {
@@ -297,7 +297,7 @@ private void ShowDiff(Dictionary<string, int> leftObjects, Dictionary<string, in
                 }
                 if (leftSize != rightSize)
                 {
-                    line.AppendFormat("{0,11}", rightSize - leftSize);
+                    line.Append($"{rightSize - leftSize,11}");
                 }
                 else
                 {