diff --git a/libc/src/__support/str_to_float.h b/libc/src/__support/str_to_float.h
--- a/libc/src/__support/str_to_float.h
+++ b/libc/src/__support/str_to_float.h
@@ -40,7 +40,7 @@
   }
 }
 
-template <class T> uint32_t leadingZeroes(T inputNumber) {
+template <class T> uint32_t inline leadingZeroes(T inputNumber) {
   // TODO(michaelrj): investigate the portability of using something like
   // __builtin_clz for specific types.
   constexpr uint32_t bitsInT = sizeof(T) * 8;
@@ -71,6 +71,14 @@
   return bitsInT - curGuess;
 }
 
+template <> uint32_t inline leadingZeroes<uint32_t>(uint32_t inputNumber) {
+  return inputNumber == 0 ? 32 : __builtin_clz(inputNumber);
+}
+
+template <> uint32_t inline leadingZeroes<uint64_t>(uint64_t inputNumber) {
+  return inputNumber == 0 ? 64 : __builtin_clzll(inputNumber);
+}
+
 static inline uint64_t low64(__uint128_t num) {
   return static_cast<uint64_t>(num & 0xffffffffffffffff);
 }
@@ -442,6 +450,81 @@
   return;
 }
 
+// Takes a mantissa and base 2 exponent and converts it into its closest
+// floating point type T equivalient. Since the exponent is already in the right
+// form, this is mostly just shifting and rounding. This is used for hexadecimal
+// numbers since a base 16 exponent multiplied by 4 is the base 2 exponent.
+template <class T>
+static inline void
+binaryExpToFloat(typename fputil::FPBits<T>::UIntType mantissa, int32_t exp2,
+                 typename fputil::FPBits<T>::UIntType *outputMantissa,
+                 uint32_t *outputExp2) {
+  using BitsType = typename fputil::FPBits<T>::UIntType;
+
+  // This is the number of leading zeroes a properly normalized float of type T
+  // should have.
+  constexpr uint32_t NORMALIZED_LEADING_ZEROES =
+      (sizeof(BitsType) * 8) - fputil::FloatProperties<T>::mantissaWidth - 1;
+  constexpr BitsType OVERFLOWED_MANTISSA =
+      BitsType(1) << (fputil::FloatProperties<T>::mantissaWidth + 1);
+
+  // Normalization
+  int32_t amountToShift =
+      NORMALIZED_LEADING_ZEROES - leadingZeroes<BitsType>(mantissa);
+  if (amountToShift < 0) {
+    mantissa <<= -amountToShift;
+  } else {
+    mantissa = shiftRightAndRound(mantissa, amountToShift);
+    if (mantissa == OVERFLOWED_MANTISSA) {
+      mantissa >>= 1;
+      exp2 += 1;
+    }
+  }
+  exp2 += amountToShift;
+
+  // Account for the fact that the mantissa represented an integer
+  // previously, but now represents the fractional part of a normalized
+  // number.
+  exp2 += fputil::FloatProperties<T>::mantissaWidth;
+
+  int32_t biasedExponent = exp2 + fputil::FPBits<T>::exponentBias;
+  // handle subnormals
+  if (biasedExponent <= 0) {
+
+    // the most mantissa is currently normalized, meaning that the msb is
+    // one bit left of where the decimal point should go.
+    amountToShift = 1;
+    BitsType mantissaCopy = mantissa >> 1;
+    while (biasedExponent < 0 && mantissaCopy > 0) {
+      mantissaCopy = mantissaCopy >> 1;
+      ++amountToShift;
+      ++biasedExponent;
+    }
+    // If we cut off any bits to fit this number into a subnormal, then it's
+    // out of range for this size of float.
+    if ((mantissa & ((1 << amountToShift) - 1)) > 0) {
+      errno = ERANGE; // NOLINT
+    }
+    mantissa = shiftRightAndRound(mantissa, amountToShift);
+    if (mantissa == OVERFLOWED_MANTISSA) {
+      mantissa >>= 1;
+      exp2 += 1;
+    } else if (mantissa == 0) {
+      biasedExponent = 0;
+    }
+  }
+  // handle numbers that're too large and get squashed to inf
+  else if (biasedExponent >
+           (1 << fputil::FloatProperties<T>::exponentWidth) - 1) {
+    // This indicates an overflow, so we make the result INF and set errno.
+    biasedExponent = (1 << fputil::FloatProperties<T>::exponentWidth) - 1;
+    mantissa = 0;
+    errno = ERANGE; // NOLINT
+  }
+  *outputMantissa = mantissa;
+  *outputExp2 = biasedExponent;
+}
+
 // checks if the next 4 characters of the string pointer are the start of a
 // hexadecimal floating point number. Does not advance the string pointer.
 static inline bool is_float_hex_start(const char *__restrict src,
@@ -456,190 +539,268 @@
   }
 }
 
-// Takes a pointer to a string and a pointer to a string pointer. This function
-// is used as the backend for all of the string to float functions.
+// Takes the start of a string representing a decimal float, as well as the
+// local decimalPoint. It returns if it suceeded in parsing any digits, and if
+// the return value is true then the outputs are pointer to the end of the
+// number, and the mantissa and exponent for the closest float T representation.
+// If the return value is false, then it is assumed that there is no number
+// here.
 template <class T>
-static inline T strtofloatingpoint(const char *__restrict src,
-                                   char **__restrict strEnd) {
+static inline bool
+decimalStringToFloat(const char *__restrict src, const char DECIMAL_POINT,
+                     char **__restrict strEnd,
+                     typename fputil::FPBits<T>::UIntType *outputMantissa,
+                     uint32_t *outputExponent) {
   using BitsType = typename fputil::FPBits<T>::UIntType;
-  fputil::FPBits<T> result = fputil::FPBits<T>();
-  const char *originalSrc = src;
+  constexpr uint32_t BASE = 10;
+  constexpr char EXPONENT_MARKER = 'e';
+
+  const char *__restrict numStart = src;
+  bool truncated = false;
   bool seenDigit = false;
-  src = first_non_whitespace(src);
+  bool afterDecimal = false;
+  BitsType mantissa = 0;
+  int32_t exponent = 0;
+
+  // The goal for the first step of parsing is to convert the number in src to
+  // the format mantissa * (base ^ exponent)
+
+  // The first loop fills the mantissa with as many digits as it can hold
+  const BitsType BITSTYPE_MAX_DIV_BY_BASE =
+      __llvm_libc::cpp::NumericLimits<BitsType>::max() / BASE;
+  while ((isdigit(*src) || *src == DECIMAL_POINT) &&
+         mantissa < BITSTYPE_MAX_DIV_BY_BASE) {
+    if (*src == DECIMAL_POINT) {
+      if (afterDecimal) {
+        break; // this means that *src points to a second decimal point, ending
+               // the number.
+      } else {
+        afterDecimal = true;
+        ++src;
+        continue;
+      }
+    }
+    uint32_t digit = *src - '0';
 
-  if (*src == '+' || *src == '-') {
-    if (*src == '-') {
-      result.setSign(true);
+    mantissa = (mantissa * BASE) + digit;
+    seenDigit = true;
+    if (afterDecimal) {
+      --exponent;
     }
+
     ++src;
   }
 
-  static constexpr char DECIMAL_POINT = '.';
-  static const char *INF_STRING = "infinity";
-  static const char *NAN_STRING = "nan";
-
-  bool truncated = false;
+  if (!seenDigit)
+    return false;
 
-  if (isdigit(*src) || *src == DECIMAL_POINT) { // regular number
-    int base = 10;
-    char exponentMarker = 'e';
-    if (is_float_hex_start(src, DECIMAL_POINT)) {
-      base = 16;
-      src += 2;
-      exponentMarker = 'p';
-      seenDigit = true;
-    }
-    const char *__restrict numStart = src;
-    bool afterDecimal = false;
-
-    BitsType mantissa = 0;
-    int32_t exponent = 0;
-
-    // The goal for the first step of parsing is to convert the number in src to
-    // the format mantissa * (base ^ exponent)
-
-    constexpr BitsType MANTISSA_MAX =
-        BitsType(1) << (fputil::FloatProperties<T>::mantissaWidth +
-                        1); // The extra bit is to give space for the implicit 1
-    const BitsType BITSTYPE_MAX_DIV_BY_BASE =
-        __llvm_libc::cpp::NumericLimits<BitsType>::max() / base;
-    while ((isalnum(*src) || *src == DECIMAL_POINT) &&
-           mantissa < BITSTYPE_MAX_DIV_BY_BASE) {
-      if (*src == DECIMAL_POINT && afterDecimal) {
+  // The second loop is to run through the remaining digits after we've filled
+  // the mantissa.
+  while (isdigit(*src) || *src == DECIMAL_POINT) {
+    if (*src == DECIMAL_POINT) {
+      if (afterDecimal) {
         break; // this means that *src points to a second decimal point, ending
                // the number.
-      } else if (*src == DECIMAL_POINT) {
+      } else {
         afterDecimal = true;
         ++src;
         continue;
       }
-      int digit = b36_char_to_int(*src);
-      if (digit >= base) {
-        break;
-      }
+    }
+    uint32_t digit = *src - '0';
 
-      mantissa = (mantissa * base) + digit;
-      seenDigit = true;
-      if (afterDecimal) {
-        --exponent;
-      }
+    if (digit > 0)
+      truncated = true;
+
+    if (!afterDecimal)
+      ++exponent;
+
+    ++src;
+  }
 
+  if ((*src | 32) == EXPONENT_MARKER) {
+    if (*(src + 1) == '+' || *(src + 1) == '-' || isdigit(*(src + 1))) {
       ++src;
+      char *tempStrEnd;
+      int32_t add_to_exponent = strtointeger<int32_t>(src, &tempStrEnd, 10);
+      if (add_to_exponent > 100000)
+        add_to_exponent = 100000;
+      else if (add_to_exponent < -100000)
+        add_to_exponent = -100000;
+
+      src = tempStrEnd;
+      exponent += add_to_exponent;
     }
+  }
+
+  *strEnd = const_cast<char *>(src);
+  if (mantissa == 0) { // if we have a 0, then also 0 the exponent.
+    *outputMantissa = 0;
+    *outputExponent = 0;
+  } else {
+    decimalExpToFloat<T>(mantissa, exponent, numStart, truncated,
+                         outputMantissa, outputExponent);
+  }
+  return true;
+}
 
-    // The second loop is to run through the remaining digits after we've filled
-    // the mantissa.
-    while (isalnum(*src) || *src == DECIMAL_POINT) {
-      if (*src == DECIMAL_POINT && afterDecimal) {
+// Takes the start of a string representing a hexadecimal float, as well as the
+// local decimal point. It returns if it suceeded in parsing any digits, and if
+// the return value is true then the outputs are pointer to the end of the
+// number, and the mantissa and exponent for the closest float T representation.
+// If the return value is false, then it is assumed that there is no number
+// here.
+template <class T>
+static inline bool
+hexadecimalStringToFloat(const char *__restrict src, const char DECIMAL_POINT,
+                         char **__restrict strEnd,
+                         typename fputil::FPBits<T>::UIntType *outputMantissa,
+                         uint32_t *outputExponent) {
+  using BitsType = typename fputil::FPBits<T>::UIntType;
+  constexpr uint32_t BASE = 16;
+  constexpr char EXPONENT_MARKER = 'p';
+
+  bool truncated = false;
+  bool seenDigit = false;
+  bool afterDecimal = false;
+  BitsType mantissa = 0;
+  int32_t exponent = 0;
+
+  // The goal for the first step of parsing is to convert the number in src to
+  // the format mantissa * (base ^ exponent)
+
+  // The first loop fills the mantissa with as many digits as it can hold
+  const BitsType BITSTYPE_MAX_DIV_BY_BASE =
+      __llvm_libc::cpp::NumericLimits<BitsType>::max() / BASE;
+  while ((isalnum(*src) || *src == DECIMAL_POINT) &&
+         mantissa < BITSTYPE_MAX_DIV_BY_BASE) {
+    if (*src == DECIMAL_POINT) {
+      if (afterDecimal) {
         break; // this means that *src points to a second decimal point, ending
                // the number.
-      } else if (*src == DECIMAL_POINT) {
+      } else {
         afterDecimal = true;
         ++src;
         continue;
       }
-      int digit = b36_char_to_int(*src);
-      if (digit >= base) {
-        break;
-      }
+    }
+    uint32_t digit = b36_char_to_int(*src);
+    if (digit >= BASE)
+      break;
 
-      if (digit > 0) {
-        truncated = true;
-      }
+    mantissa = (mantissa * BASE) + digit;
+    seenDigit = true;
+    if (afterDecimal)
+      --exponent;
+
+    ++src;
+  }
 
-      if (!afterDecimal) {
-        exponent++;
+  if (!seenDigit)
+    return false;
+
+  // The second loop is to run through the remaining digits after we've filled
+  // the mantissa.
+  while (isalnum(*src) || *src == DECIMAL_POINT) {
+    if (*src == DECIMAL_POINT) {
+      if (afterDecimal) {
+        break; // this means that *src points to a second decimal point, ending
+               // the number.
+      } else {
+        afterDecimal = true;
+        ++src;
+        continue;
       }
+    }
+    uint32_t digit = b36_char_to_int(*src);
+    if (digit >= BASE)
+      break;
+
+    if (digit > 0)
+      truncated = true;
+
+    if (!afterDecimal)
+      ++exponent;
 
+    ++src;
+  }
+
+  // Convert the exponent from having a base of 16 to having a base of 2.
+  exponent *= 4;
+
+  if ((*src | 32) == EXPONENT_MARKER) {
+    if (*(src + 1) == '+' || *(src + 1) == '-' || isdigit(*(src + 1))) {
       ++src;
+      char *tempStrEnd;
+      int32_t add_to_exponent = strtointeger<int32_t>(src, &tempStrEnd, 10);
+      if (add_to_exponent > 100000)
+        add_to_exponent = 100000;
+      else if (add_to_exponent < -100000)
+        add_to_exponent = -100000;
+      src = tempStrEnd;
+      exponent += add_to_exponent;
     }
+  }
+  *strEnd = const_cast<char *>(src);
+  if (mantissa == 0) { // if we have a 0, then also 0 the exponent.
+    *outputMantissa = 0;
+    *outputExponent = 0;
+  } else {
+    binaryExpToFloat<T>(mantissa, exponent, outputMantissa, outputExponent);
+  }
+  return true;
+}
 
-    // if our base is 16 then convert the exponent to base 2
-    if (base == 16) {
-      exponent *= 4;
-    }
+// Takes a pointer to a string and a pointer to a string pointer. This function
+// is used as the backend for all of the string to float functions.
+template <class T>
+static inline T strtofloatingpoint(const char *__restrict src,
+                                   char **__restrict strEnd) {
+  using BitsType = typename fputil::FPBits<T>::UIntType;
+  fputil::FPBits<T> result = fputil::FPBits<T>();
+  const char *originalSrc = src;
+  bool seenDigit = false;
+  src = first_non_whitespace(src);
 
-    if ((*src | 32) == exponentMarker) {
-      if (*(src + 1) == '+' || *(src + 1) == '-' || isdigit(*(src + 1))) {
-        ++src;
-        char *tempStrEnd;
-        int32_t add_to_exponent = strtointeger<int32_t>(src, &tempStrEnd, 10);
-        if (add_to_exponent > 100000) {
-          add_to_exponent = 100000;
-        } else if (add_to_exponent < -100000) {
-          add_to_exponent = -100000;
-        }
-        src += tempStrEnd - src;
-        exponent += add_to_exponent;
-      }
+  if (*src == '+' || *src == '-') {
+    if (*src == '-') {
+      result.setSign(true);
     }
+    ++src;
+  }
 
-    if (mantissa == 0) { // if we have a 0, then also 0 the exponent.
-      exponent = 0;
-    } else if (base == 16) {
-
-      // These two loops should normalize the number if we assume the decimal
-      // point is after the bit at mantissaWidth.
-      // For example if type T is a 32 bit float, this should result in a
-      // mantissa with its most significant 1 being at bit 23.
-      while (mantissa < (MANTISSA_MAX >> 1)) {
-        mantissa = mantissa << 1;
-        --exponent;
-      }
-      BitsType mantissaCopy = mantissa;
-      unsigned int amountToShift = 0;
-      while (mantissaCopy > MANTISSA_MAX) {
-        mantissaCopy = mantissaCopy >> 1;
-        ++amountToShift;
-      }
-      exponent += amountToShift;
-      mantissa = shiftRightAndRound(mantissa, amountToShift);
-
-      // Account for the fact that the mantissa represented an integer
-      // previously, but now represents the fractional part of a normalized
-      // number.
-      exponent += fputil::FloatProperties<T>::mantissaWidth;
-
-      int32_t biasedExponent = exponent + fputil::FPBits<T>::exponentBias;
-      if (biasedExponent <= 0) {
-        // handle subnormals here
-
-        // the most mantissa is currently normalized, meaning that the msb is
-        // one bit left of where the decimal point should go.
-        amountToShift = 1;
-        mantissaCopy = mantissa >> 1;
-        while (biasedExponent < 0 && mantissaCopy > 0) {
-          mantissaCopy = mantissaCopy >> 1;
-          ++amountToShift;
-          ++biasedExponent;
-        }
-        // If we cut off any bits to fit this number into a subnormal, then it's
-        // out of range for this size of float.
-        if ((mantissa & ((1 << amountToShift) - 1)) > 0) {
-          errno = ERANGE; // NOLINT
-        }
-        mantissa = shiftRightAndRound(mantissa, amountToShift);
-        if (mantissa == 0) {
-          biasedExponent = 0;
-        }
-      } else if (biasedExponent > result.maxExponent) {
-        // This indicates an overflow, so we make the result INF and set errno.
-        biasedExponent = result.maxExponent;
-        mantissa = 0;
-        errno = ERANGE; // NOLINT
-      }
+  static constexpr char DECIMAL_POINT = '.';
+  static const char *INF_STRING = "infinity";
+  static const char *NAN_STRING = "nan";
+
+  // bool truncated = false;
 
-      result.setUnbiasedExponent(biasedExponent);
-      result.setMantissa(mantissa);
+  if (isdigit(*src) || *src == DECIMAL_POINT) { // regular number
+    int base = 10;
+    char exponentMarker = 'e';
+    if (is_float_hex_start(src, DECIMAL_POINT)) {
+      base = 16;
+      src += 2;
+      exponentMarker = 'p';
+      seenDigit = true;
+    }
+    char *newStrEnd = nullptr;
+
+    BitsType outputMantissa = 0;
+    uint32_t outputExponent = 0;
+    if (base == 16) {
+      seenDigit = hexadecimalStringToFloat<T>(src, DECIMAL_POINT, &newStrEnd,
+                                              &outputMantissa, &outputExponent);
     } else { // base is 10
-      BitsType outputMantissa = 0;
-      uint32_t outputExponent = 0;
-      decimalExpToFloat<T>(mantissa, exponent, numStart, truncated,
-                           &outputMantissa, &outputExponent);
+      seenDigit = decimalStringToFloat<T>(src, DECIMAL_POINT, &newStrEnd,
+                                          &outputMantissa, &outputExponent);
+    }
+
+    if (seenDigit) {
+      src += newStrEnd - src;
       result.setMantissa(outputMantissa);
       result.setUnbiasedExponent(outputExponent);
     }
-
   } else if ((*src | 32) == 'n') { // NaN
     if ((src[1] | 32) == NAN_STRING[1] && (src[2] | 32) == NAN_STRING[2]) {
       seenDigit = true;
diff --git a/libc/test/src/stdlib/strtof_test.cpp b/libc/test/src/stdlib/strtof_test.cpp
--- a/libc/test/src/stdlib/strtof_test.cpp
+++ b/libc/test/src/stdlib/strtof_test.cpp
@@ -132,6 +132,10 @@
   runTest("0x123456700", 11, 0x4f91a2b4);
 }
 
+TEST_F(LlvmLibcStrToFTest, HexadecimalsWithRoundingProblems) {
+  runTest("0xFFFFFFFF", 10, 0x4f800000);
+}
+
 TEST_F(LlvmLibcStrToFTest, HexadecimalOutOfRangeTests) {
   runTest("0x123456789123456789123456789123456789", 38, 0x7f800000, ERANGE);
   runTest("-0x123456789123456789123456789123456789", 39, 0xff800000, ERANGE);