diff --git a/include/nlohmann/detail/conversions/to_chars.hpp b/include/nlohmann/detail/conversions/to_chars.hpp
index d99703a5..a7856253 100644
--- a/include/nlohmann/detail/conversions/to_chars.hpp
+++ b/include/nlohmann/detail/conversions/to_chars.hpp
@@ -990,11 +990,11 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
         // digits[000]
         // len <= max_exp + 2
 
-        std::memset(buf + k, '0', static_cast<size_t>(n - k));
+        std::memset(buf + k, '0', static_cast<size_t>(n) - static_cast<size_t>(k));
         // Make it look like a floating-point number (#362, #378)
         buf[n + 0] = '.';
         buf[n + 1] = '0';
-        return buf + (n + 2);
+        return buf + (static_cast<size_t>(n) + 2);
     }
 
     if (0 < n and n <= max_exp)
@@ -1004,9 +1004,9 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
 
         assert(k > n);
 
-        std::memmove(buf + (n + 1), buf + n, static_cast<size_t>(k - n));
+        std::memmove(buf + (static_cast<size_t>(n) + 1), buf + n, static_cast<size_t>(k) - static_cast<size_t>(n));
         buf[n] = '.';
-        return buf + (k + 1);
+        return buf + (static_cast<size_t>(k) + 1);
     }
 
     if (min_exp < n and n <= 0)
@@ -1014,11 +1014,11 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
         // 0.[000]digits
         // len <= 2 + (-min_exp - 1) + max_digits10
 
-        std::memmove(buf + (2 + -n), buf, static_cast<size_t>(k));
+        std::memmove(buf + (2 + static_cast<size_t>(-n)), buf, static_cast<size_t>(k));
         buf[0] = '0';
         buf[1] = '.';
         std::memset(buf + 2, '0', static_cast<size_t>(-n));
-        return buf + (2 + (-n) + k);
+        return buf + (2 + static_cast<size_t>(-n) + k);
     }
 
     if (k == 1)
@@ -1033,9 +1033,9 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
         // d.igitsE+123
         // len <= max_digits10 + 1 + 5
 
-        std::memmove(buf + 2, buf + 1, static_cast<size_t>(k - 1));
+        std::memmove(buf + 2, buf + 1, static_cast<size_t>(k) - 1);
         buf[1] = '.';
-        buf += 1 + k;
+        buf += 1 + static_cast<size_t>(k);
     }
 
     *buf++ = 'e';
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 3152db0b..47861346 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -14527,11 +14527,11 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
         // digits[000]
         // len <= max_exp + 2
 
-        std::memset(buf + k, '0', static_cast<size_t>(n - k));
+        std::memset(buf + k, '0', static_cast<size_t>(n) - static_cast<size_t>(k));
         // Make it look like a floating-point number (#362, #378)
         buf[n + 0] = '.';
         buf[n + 1] = '0';
-        return buf + (n + 2);
+        return buf + (static_cast<size_t>(n) + 2);
     }
 
     if (0 < n and n <= max_exp)
@@ -14541,9 +14541,9 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
 
         assert(k > n);
 
-        std::memmove(buf + (n + 1), buf + n, static_cast<size_t>(k - n));
+        std::memmove(buf + (static_cast<size_t>(n) + 1), buf + n, static_cast<size_t>(k) - static_cast<size_t>(n));
         buf[n] = '.';
-        return buf + (k + 1);
+        return buf + (static_cast<size_t>(k) + 1);
     }
 
     if (min_exp < n and n <= 0)
@@ -14551,11 +14551,11 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
         // 0.[000]digits
         // len <= 2 + (-min_exp - 1) + max_digits10
 
-        std::memmove(buf + (2 + -n), buf, static_cast<size_t>(k));
+        std::memmove(buf + (2 + static_cast<size_t>(-n)), buf, static_cast<size_t>(k));
         buf[0] = '0';
         buf[1] = '.';
         std::memset(buf + 2, '0', static_cast<size_t>(-n));
-        return buf + (2 + (-n) + k);
+        return buf + (2 + static_cast<size_t>(-n) + k);
     }
 
     if (k == 1)
@@ -14570,9 +14570,9 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
         // d.igitsE+123
         // len <= max_digits10 + 1 + 5
 
-        std::memmove(buf + 2, buf + 1, static_cast<size_t>(k - 1));
+        std::memmove(buf + 2, buf + 1, static_cast<size_t>(k) - 1);
         buf[1] = '.';
-        buf += 1 + k;
+        buf += 1 + static_cast<size_t>(k);
     }
 
     *buf++ = 'e';