diff --git a/src/DividingCoder.cs b/src/DividingCoder.cs
index 1399b72..ffd4f27 100644
--- a/src/DividingCoder.cs
+++ b/src/DividingCoder.cs
@@ -23,7 +23,7 @@ public abstract class DividingCoder<TAlphabet>(TAlphabet alphabet)
     : IBaseCoder, INonAllocatingBaseCoder
     where TAlphabet: CodingAlphabet
 {
-    readonly int reductionFactor = Convert.ToInt32(1000 * Math.Log2(alphabet.Length) / 8);
+    readonly int reductionFactor = Convert.ToInt32(10_000 * Math.Log2(alphabet.Length) / 8);
     readonly char zeroChar = alphabet.Value[0];
 
     /// <summary>
@@ -40,7 +40,7 @@ public virtual int GetSafeByteCountForDecoding(ReadOnlySpan<char> text)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     int getSafeByteCountForDecoding(int textLen, int zeroPrefixLen)
     {
-        return zeroPrefixLen + ((textLen - zeroPrefixLen) * reductionFactor / 1000) + 1;
+        return zeroPrefixLen + ((textLen - zeroPrefixLen) * reductionFactor / 10_000) + 1;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -62,7 +62,7 @@ public virtual int GetSafeCharCountForEncoding(ReadOnlySpan<byte> bytes)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     int getSafeCharCountForEncoding(int bytesLen, int zeroPrefixLen)
     {
-        return zeroPrefixLen + ((bytesLen - zeroPrefixLen) * 1000 / reductionFactor) + 1;
+        return zeroPrefixLen + ((bytesLen - zeroPrefixLen) * 10_000 / reductionFactor) + 1;
     }
 
     /// <summary>
diff --git a/test/Base62/DefaultTest.cs b/test/Base62/DefaultTest.cs
index 20143ef..159ea09 100644
--- a/test/Base62/DefaultTest.cs
+++ b/test/Base62/DefaultTest.cs
@@ -61,5 +61,20 @@ public void TryDecode_ReturnsCorrectValues(string decoded, string encoded)
         Assert.That(result, Is.True);
         Assert.That(Encoding.UTF8.GetString(output[..bytesWritten]), Is.EqualTo(decoded));
     }
-
+    
+    [Test]
+    public void Roundtrip_DoesNotTruncateHighByte()
+    {
+        // https://github.com/ssg/SimpleBase/issues/79
+        
+        // 2762 is the smallest length where (textLen * 744 / 1000) + 1 underestimates
+        // the required output buffer by 1, dropping the most-significant byte.
+        var bytes = new byte[2762];
+        Array.Fill(bytes, (byte)0xFF);
+        
+        var encoded = Base62.Default.Encode(bytes);
+        var decoded = Base62.Default.Decode(encoded);
+        
+        Assert.That(decoded, Is.EqualTo(bytes));
+    }
 }