diff --git a/CHANGELOG.md b/CHANGELOG.md
index b2cc4d6c9a..d284cd8092 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - Print Area and Row Break. [Issue #1275](https://github.com/PHPOffice/PhpSpreadsheet/issues/1275) [PR #4450](https://github.com/PHPOffice/PhpSpreadsheet/pull/4450)
 - Copy Styles after insertNewColumnBefore. [Issue #1425](https://github.com/PHPOffice/PhpSpreadsheet/issues/1425) [PR #4468](https://github.com/PHPOffice/PhpSpreadsheet/pull/4468)
 - Xls Writer Treat Hyperlink Starting with # as Internal. [Issue #56](https://github.com/PHPOffice/PhpSpreadsheet/issues/56) [PR #4453](https://github.com/PHPOffice/PhpSpreadsheet/pull/4453)
+- More Precision for Float to String Casts. [Issue #3899](https://github.com/PHPOffice/PhpSpreadsheet/issues/3899) [PR #4479](https://github.com/PHPOffice/PhpSpreadsheet/pull/4479)
 - Hyperlink Styles. [Issue #1632](https://github.com/PHPOffice/PhpSpreadsheet/issues/1632) [PR #4478](https://github.com/PHPOffice/PhpSpreadsheet/pull/4478)
 - ODS Handling of Ceiling and Floor. [Issue #477](https://github.com/PHPOffice/PhpSpreadsheet/issues/407) [PR #4466](https://github.com/PHPOffice/PhpSpreadsheet/pull/4466)
 - Xlsx Reader Do Not Process Printer Settings for Dataonly. [Issue #4477](https://github.com/PHPOffice/PhpSpreadsheet/issues/4477) [PR #4480](https://github.com/PHPOffice/PhpSpreadsheet/pull/4480)
diff --git a/src/PhpSpreadsheet/Shared/Date.php b/src/PhpSpreadsheet/Shared/Date.php
index e8f23164f3..3767a60118 100644
--- a/src/PhpSpreadsheet/Shared/Date.php
+++ b/src/PhpSpreadsheet/Shared/Date.php
@@ -471,7 +471,7 @@ public static function stringToExcel(string $dateValue): bool|float
         if (strlen($dateValue) < 2) {
             return false;
         }
-        if (!preg_match('/^(\d{1,4}[ \.\/\-][A-Z]{3,9}([ \.\/\-]\d{1,4})?|[A-Z]{3,9}[ \.\/\-]\d{1,4}([ \.\/\-]\d{1,4})?|\d{1,4}[ \.\/\-]\d{1,4}([ \.\/\-]\d{1,4})?)( \d{1,2}:\d{1,2}(:\d{1,2})?)?$/iu', $dateValue)) {
+        if (!preg_match('/^(\d{1,4}[ \.\/\-][A-Z]{3,9}([ \.\/\-]\d{1,4})?|[A-Z]{3,9}[ \.\/\-]\d{1,4}([ \.\/\-]\d{1,4})?|\d{1,4}[ \.\/\-]\d{1,4}([ \.\/\-]\d{1,4})?)( \d{1,2}:\d{1,2}(:\d{1,2}([.]\d+))?)?$/iu', $dateValue)) {
             return false;
         }
 
diff --git a/src/PhpSpreadsheet/Shared/StringHelper.php b/src/PhpSpreadsheet/Shared/StringHelper.php
index 40adfd8c96..3e4311832c 100644
--- a/src/PhpSpreadsheet/Shared/StringHelper.php
+++ b/src/PhpSpreadsheet/Shared/StringHelper.php
@@ -2,6 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheet\Shared;
 
+use Composer\Pcre\Preg;
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
 use Stringable;
@@ -494,9 +495,9 @@ public static function mbStrSplit(string $string): array
     {
         // Split at all position not after the start: ^
         // and not before the end: $
-        $split = preg_split('/(?<!^)(?!$)/u', $string);
+        $split = Preg::split('/(?<!^)(?!$)/u', $string);
 
-        return ($split === false) ? [] : $split;
+        return $split;
     }
 
     /**
@@ -530,6 +531,7 @@ private static function getLocaleValue(string $key, string $altKey, string $defa
         $localeconv = localeconv();
         $rslt = $localeconv[$key];
         // win-1252 implements Euro as 0x80 plus other symbols
+        // Not suitable for Composer\Pcre\Preg
         if (preg_match('//u', $rslt) !== 1) {
             $rslt = '';
         }
@@ -659,6 +661,22 @@ public static function convertToString(mixed $value, bool $throw = true, string
         if ($convertBool && is_bool($value)) {
             return $value ? Calculation::getTRUE() : Calculation::getFALSE();
         }
+        if (is_float($value)) {
+            $string = (string) $value;
+            // look out for scientific notation
+            if (!Preg::isMatch('/[^-+0-9.]/', $string)) {
+                $minus = $value < 0 ? '-' : '';
+                $positive = abs($value);
+                $floor = floor($positive);
+                $oldFrac = (string) ($positive - $floor);
+                $frac = Preg::replace('/^0[.](\d+)$/', '$1', $oldFrac);
+                if ($frac !== $oldFrac) {
+                    return "$minus$floor.$frac";
+                }
+            }
+
+            return $string;
+        }
         if ($value === null || is_scalar($value) || $value instanceof Stringable) {
             return (string) $value;
         }
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
index 5ca5911a28..d8e64ad4d7 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
@@ -1463,15 +1463,11 @@ private function writeCellString(XMLWriter $objWriter, string $mappedType, RichT
 
     private function writeCellNumeric(XMLWriter $objWriter, float|int $cellValue): void
     {
-        //force a decimal to be written if the type is float
-        if (is_float($cellValue)) {
-            // force point as decimal separator in case current locale uses comma
-            $cellValue = str_replace(',', '.', (string) $cellValue);
-            if (!str_contains($cellValue, '.')) {
-                $cellValue = $cellValue . '.0';
-            }
+        $result = StringHelper::convertToString($cellValue);
+        if (is_float($cellValue) && !str_contains($result, '.')) {
+            $result .= '.0';
         }
-        $objWriter->writeElement('v', "$cellValue");
+        $objWriter->writeElement('v', $result);
     }
 
     private function writeCellBoolean(XMLWriter $objWriter, string $mappedType, bool $cellValue): void
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php
index 0f6bd0b977..31a1607945 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php
@@ -54,8 +54,9 @@ public function testTooMuchPrecision(mixed $expectedResult, float|int|string $va
         $sheet = $this->getSheet();
         $sheet->getCell('E1')->setValue($value);
         $sheet->getCell('E2')->setValue("=TRUNC(E1,$digits)");
-        $result = $sheet->getCell('E2')->getCalculatedValueString();
-        self::assertSame($expectedResult, $result);
+        /** @var float|string */
+        $result = $sheet->getCell('E2')->getCalculatedValue();
+        self::assertSame($expectedResult, (string) $result);
     }
 
     public static function providerTooMuchPrecision(): array
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php
index 3ec22ddda4..2979463327 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php
@@ -4,6 +4,7 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
+use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use PHPUnit\Framework\Attributes\DataProvider;
 
 class ArrayToTextTest extends AllSetupTeardown
@@ -17,6 +18,9 @@ public function testArrayToText(string $expectedResult, array $testData, int $mo
         $worksheet->getCell('H1')->setValue("=ARRAYTOTEXT(A1:C5, {$mode})");
 
         $result = $worksheet->getCell('H1')->getCalculatedValue();
+        $b1SimpleCast = '12345.6789';
+        $b1AccurateCast = StringHelper::convertToString(12345.6789);
+        $expectedResult = str_replace($b1SimpleCast, $b1AccurateCast, $expectedResult);
         self::assertSame($expectedResult, $result);
     }
 
diff --git a/tests/PhpSpreadsheetTests/FloatImprecisionTest.php b/tests/PhpSpreadsheetTests/FloatImprecisionTest.php
new file mode 100644
index 0000000000..aa960486b3
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/FloatImprecisionTest.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+class FloatImprecisionTest extends TestCase
+{
+    #[DataProvider('providerFloats')]
+    public function testCompareFloats(float $float1, float $float2): void
+    {
+        self::assertSame($float1, $float2);
+    }
+
+    public static function providerFloats(): array
+    {
+        return [
+            [12345.6789, 12345.67890000000079],
+        ];
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php b/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php
index 1bc54c3f62..9ec2138c89 100644
--- a/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php
@@ -32,7 +32,9 @@ protected function setUp(): void
         parent::setUp();
 
         $this->compatibilityMode = Functions::getCompatibilityMode();
-        Functions::setCompatibilityMode(Functions::COMPATIBILITY_OPENOFFICE);
+        Functions::setCompatibilityMode(
+            Functions::COMPATIBILITY_OPENOFFICE
+        );
     }
 
     protected function tearDown(): void
@@ -57,6 +59,8 @@ public function testWriteSpreadsheet(): void
         $worksheet1 = $workbook->getActiveSheet();
         $worksheet1->setCellValue('A1', 1); // Number
         $worksheet1->setCellValue('B1', 12345.6789); // Number
+        $b1SimpleCast = '12345.6789';
+        $b1AccurateCast = StringHelper::convertToString(12345.6789);
         $worksheet1->setCellValue('C1', '1'); // Number without cast
         $worksheet1->setCellValueExplicit('D1', '01234', DataType::TYPE_STRING); // Number casted to string
         $worksheet1->setCellValue('E1', 'Lorem ipsum'); // String
@@ -74,6 +78,11 @@ public function testWriteSpreadsheet(): void
         $worksheet1->getStyle('D2')
             ->getNumberFormat()
             ->setFormatCode(NumberFormat::FORMAT_DATE_DATETIME);
+        /** @var float */
+        $d2SimpleCast = $worksheet1->getCell('D2')->getValue();
+        $d2SimpleCast = (string) $d2SimpleCast;
+        $d2AccurateCast = $worksheet1
+            ->getCell('D2')->getValueString();
 
         $worksheet1->setCellValueExplicit('F1', null, DataType::TYPE_ERROR);
         $worksheet1->setCellValueExplicit('G1', 'Lorem ipsum', DataType::TYPE_INLINE);
@@ -85,12 +94,17 @@ public function testWriteSpreadsheet(): void
         $worksheet1->getStyle('C1')->getFont()->setSize(14);
         $worksheet1->getStyle('C1')->getFont()->setColor(new Color(Color::COLOR_BLUE));
 
-        $worksheet1->getStyle('C1')->getFill()->setFillType(Fill::FILL_SOLID);
-        $worksheet1->getStyle('C1')->getFill()->setStartColor(new Color(Color::COLOR_RED));
+        $worksheet1->getStyle('C1')
+            ->getFill()->setFillType(Fill::FILL_SOLID);
+        $worksheet1->getStyle('C1')
+            ->getFill()->setStartColor(new Color(Color::COLOR_RED));
 
-        $worksheet1->getStyle('C1')->getFont()->setUnderline(Font::UNDERLINE_SINGLE);
-        $worksheet1->getStyle('C2')->getFont()->setUnderline(Font::UNDERLINE_DOUBLE);
-        $worksheet1->getStyle('D2')->getFont()->setUnderline(Font::UNDERLINE_NONE);
+        $worksheet1->getStyle('C1')->getFont()
+            ->setUnderline(Font::UNDERLINE_SINGLE);
+        $worksheet1->getStyle('C2')->getFont()
+            ->setUnderline(Font::UNDERLINE_DOUBLE);
+        $worksheet1->getStyle('D2')->getFont()
+            ->setUnderline(Font::UNDERLINE_NONE);
 
         // Worksheet 2
         $worksheet2 = $workbook->createSheet();
@@ -101,7 +115,12 @@ public function testWriteSpreadsheet(): void
         $content = new Content(new Ods($workbook));
         $xml = $content->write();
 
-        self::assertXmlStringEqualsXmlFile($this->samplesPath . '/content-with-data.xml', $xml);
+        $xmlFile = $this->samplesPath . '/content-with-data.xml';
+        $xmlContents = (string) file_get_contents($xmlFile);
+        $xmlContents = str_replace($b1SimpleCast, $b1AccurateCast, $xmlContents);
+        $xmlContents = str_replace($d2SimpleCast, $d2AccurateCast, $xmlContents);
+        self::assertXmlStringEqualsXmlString($xmlContents, $xml);
+        $workbook->disconnectWorksheets();
     }
 
     public function testWriteWithHiddenWorksheet(): void
@@ -124,19 +143,21 @@ public function testWriteWithHiddenWorksheet(): void
         $xml = $content->write();
 
         self::assertXmlStringEqualsXmlFile($this->samplesPath . '/content-hidden-worksheet.xml', $xml);
+        $workbook->disconnectWorksheets();
     }
 
     public function testWriteBorderStyle(): void
     {
         $spreadsheet = new Spreadsheet();
-        $spreadsheet->getActiveSheet()->getStyle('A1:B2')->applyFromArray([
-            'borders' => [
-                'outline' => [
-                    'borderStyle' => Border::BORDER_THICK,
-                    'color' => ['argb' => 'AA22DD00'],
+        $spreadsheet->getActiveSheet()
+            ->getStyle('A1:B2')->applyFromArray([
+                'borders' => [
+                    'outline' => [
+                        'borderStyle' => Border::BORDER_THICK,
+                        'color' => ['argb' => 'AA22DD00'],
+                    ],
                 ],
-            ],
-        ]);
+            ]);
 
         $content = new Content(new Ods($spreadsheet));
         $xml = $content->write();
@@ -161,5 +182,6 @@ public function testWriteBorderStyle(): void
                 }
             }
         }
+        $spreadsheet->disconnectWorksheets();
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Writer/Ods/MicrosecondsTest.php b/tests/PhpSpreadsheetTests/Writer/Ods/MicrosecondsTest.php
new file mode 100644
index 0000000000..70db6fd806
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Ods/MicrosecondsTest.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Ods;
+
+use DateTime;
+use PhpOffice\PhpSpreadsheet\Shared\Date;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class MicrosecondsTest extends AbstractFunctional
+{
+    /**
+     * Test save and load XLSX file for round-trip DateTime.
+     * Ods Writer does not support date formats,
+     * and Reader does not support styles, so this
+     * test is slightly different than its Xls/Xlsx counterparts.
+     */
+    public function testIssue4476(): void
+    {
+        $date = '2020-10-21';
+        $time = '14:55:31';
+        $originalDateTime = new DateTime("{$date}T{$time}");
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setCellValue('A1', Date::dateTimeToExcel($originalDateTime));
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Ods');
+        $spreadsheet->disconnectWorksheets();
+
+        $rsheet = $reloadedSpreadsheet->getActiveSheet();
+        $rsheet->getStyle('A1')
+            ->getNumberFormat()
+            ->setFormatCode('yyyy-mm-dd hh:mm:ss.000');
+        /** @var float */
+        $reread = $rsheet->getCell('A1')->getValue();
+        $temp = Date::excelToDateTimeObject($reread)
+            ->format('Y-m-d H:i:s.u');
+        self::assertSame("{$date} {$time}.000000", $temp, 'round trip works with float value');
+        $formatted = $rsheet->getCell('A1')->getFormattedValue();
+        self::assertSame("{$date} {$time}.000", $formatted, 'round trip works with formatted value');
+        /** @var float */
+        $temp = Date::stringToExcel($formatted);
+        $temp = Date::excelToDateTimeObject($temp)
+            ->format('Y-m-d H:i:s.u');
+        self::assertSame("{$date} {$time}.000000", $temp, 'round trip works using stringToExcel on formatted value');
+
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/MicrosecondsTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/MicrosecondsTest.php
new file mode 100644
index 0000000000..130d6a401e
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/MicrosecondsTest.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
+
+use DateTime;
+use PhpOffice\PhpSpreadsheet\Shared\Date;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class MicrosecondsTest extends AbstractFunctional
+{
+    /**
+     * Test save and load XLSX file for round-trip DateTime.
+     */
+    public function testIssue4476(): void
+    {
+        $date = '2020-10-21';
+        $time = '14:55:31';
+        $originalDateTime = new DateTime("{$date}T{$time}");
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setCellValue('A1', Date::dateTimeToExcel($originalDateTime));
+        $sheet->getStyle('A1')
+            ->getNumberFormat()
+            ->setFormatCode('yyyy-mm-dd hh:mm:ss.000');
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xls');
+        $spreadsheet->disconnectWorksheets();
+
+        $rsheet = $reloadedSpreadsheet->getActiveSheet();
+        /** @var float */
+        $reread = $rsheet->getCell('A1')->getValue();
+        $temp = Date::excelToDateTimeObject($reread)
+            ->format('Y-m-d H:i:s.u');
+        self::assertSame("{$date} {$time}.000000", $temp, 'round trip works with float value');
+        $formatted = $rsheet->getCell('A1')->getFormattedValue();
+        self::assertSame("{$date} {$time}.000", $formatted, 'round trip works with formatted value');
+        /** @var float */
+        $temp = Date::stringToExcel($formatted);
+        $temp = Date::excelToDateTimeObject($temp)
+            ->format('Y-m-d H:i:s.u');
+        self::assertSame("{$date} {$time}.000000", $temp, 'round trip works using stringToExcel on formatted value');
+
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/MicrosecondsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/MicrosecondsTest.php
new file mode 100644
index 0000000000..bdc50bf8cd
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/MicrosecondsTest.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
+
+use DateTime;
+use PhpOffice\PhpSpreadsheet\Shared\Date;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class MicrosecondsTest extends AbstractFunctional
+{
+    /**
+     * Test save and load XLSX file for round-trip DateTime.
+     */
+    public function testIssue4476(): void
+    {
+        $date = '2020-10-21';
+        $time = '14:55:31';
+        $originalDateTime = new DateTime("{$date}T{$time}");
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setCellValue('A1', Date::dateTimeToExcel($originalDateTime));
+        $sheet->getStyle('A1')
+            ->getNumberFormat()
+            ->setFormatCode('yyyy-mm-dd hh:mm:ss.000');
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xlsx');
+        $spreadsheet->disconnectWorksheets();
+
+        $rsheet = $reloadedSpreadsheet->getActiveSheet();
+        /** @var float */
+        $reread = $rsheet->getCell('A1')->getValue();
+        $temp = Date::excelToDateTimeObject($reread)
+            ->format('Y-m-d H:i:s.u');
+        self::assertSame("{$date} {$time}.000000", $temp, 'round trip works with float value');
+        $formatted = $rsheet->getCell('A1')->getFormattedValue();
+        self::assertSame("{$date} {$time}.000", $formatted, 'round trip works with formatted value');
+        /** @var float */
+        $temp = Date::stringToExcel($formatted);
+        $temp = Date::excelToDateTimeObject($temp)
+            ->format('Y-m-d H:i:s.u');
+        self::assertSame("{$date} {$time}.000000", $temp, 'round trip works using stringToExcel on formatted value');
+
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+}