diff --git a/box.go b/box.go
index 427d329..9cbcd7c 100644
--- a/box.go
+++ b/box.go
@@ -2,7 +2,7 @@ package gopdf
 
 type Box struct {
 	Left, Top, Right, Bottom float64
-	unitOverride             int
+	unitOverride             defaultUnitConfig
 }
 
 // UnitsToPoints converts the box coordinates to Points. When this is called it is assumed the values of the box are in Units
@@ -11,8 +11,9 @@ func (box *Box) UnitsToPoints(t int) (b *Box) {
 		return
 	}
 
-	if box.unitOverride != UnitUnset {
-		t = box.unitOverride
+	unitCfg := defaultUnitConfig{Unit: t}
+	if box.unitOverride.getUnit() != UnitUnset {
+		unitCfg = box.unitOverride
 	}
 
 	b = &Box{
@@ -21,6 +22,25 @@ func (box *Box) UnitsToPoints(t int) (b *Box) {
 		Right:  box.Right,
 		Bottom: box.Bottom,
 	}
-	UnitsToPointsVar(t, &b.Left, &b.Top, &b.Right, &b.Bottom)
+	unitsToPointsVar(unitCfg, &b.Left, &b.Top, &b.Right, &b.Bottom)
+	return
+}
+
+func (box *Box) unitsToPoints(unitCfg unitConfigurator) (b *Box) {
+	if box == nil {
+		return
+	}
+
+	if box.unitOverride.getUnit() != UnitUnset {
+		unitCfg = box.unitOverride
+	}
+
+	b = &Box{
+		Left:   box.Left,
+		Top:    box.Top,
+		Right:  box.Right,
+		Bottom: box.Bottom,
+	}
+	unitsToPointsVar(unitCfg, &b.Left, &b.Top, &b.Right, &b.Bottom)
 	return
 }
diff --git a/config.go b/config.go
index 7dc5558..a497f53 100644
--- a/config.go
+++ b/config.go
@@ -14,6 +14,10 @@ const (
 	conversionUnitMM = 72.0 / 25.4
 	conversionUnitCM = 72.0 / 2.54
 	conversionUnitIN = 72.0
+	//We use a dpi of 96 dpi as the default, so we get a conversionUnitPX = 3.0 / 4.0, which comes from 72.0 / 96.0.
+	//If you want to change this value, you can change it at Config.ConversionForUnit
+	//example: If you use dpi at 300.0
+	//pdf.Start(gopdf.Config{PageSize: gopdf.Rect{W: 595.28, H: 841.89}, ConversionForUnit: 72.0 / 300.0 })
 	conversionUnitPX = 3.0 / 4.0
 )
 
@@ -30,11 +34,22 @@ const (
 
 // Config static config
 type Config struct {
-	Unit       int                 // The unit type to use when composing the document.
-	TrimBox    Box                 // The default trim box for all pages in the document
-	PageSize   Rect                // The default page size for all pages in the document
-	K          float64             // Not sure
-	Protection PDFProtectionConfig // Protection settings
+	Unit int // The unit type to use when composing the document.
+	//Value that use to convert units to points.
+	//If this variable is not 0. This value will be used to calculate the unit conversion instead of the existing const value in the system.
+	//And if this variable is not 0. Value ​​in Config.Unit will not be used.
+	ConversionForUnit float64
+	TrimBox           Box                 // The default trim box for all pages in the document
+	PageSize          Rect                // The default page size for all pages in the document
+	K                 float64             // Not sure
+	Protection        PDFProtectionConfig // Protection settings
+}
+
+func (c Config) getUnit() int {
+	return c.Unit
+}
+func (c Config) getConversionForUnit() float64 {
+	return c.ConversionForUnit
 }
 
 // PDFProtectionConfig config of pdf protection
@@ -47,7 +62,14 @@ type PDFProtectionConfig struct {
 
 // UnitsToPoints converts units of the provided type to points
 func UnitsToPoints(t int, u float64) float64 {
-	switch t {
+	return unitsToPoints(defaultUnitConfig{Unit: t}, u)
+}
+
+func unitsToPoints(unitCfg unitConfigurator, u float64) float64 {
+	if unitCfg.getConversionForUnit() != 0 {
+		return u * unitCfg.getConversionForUnit()
+	}
+	switch unitCfg.getUnit() {
 	case UnitPT:
 		return u * conversionUnitPT
 	case UnitMM:
@@ -65,7 +87,14 @@ func UnitsToPoints(t int, u float64) float64 {
 
 // PointsToUnits converts points to the provided units
 func PointsToUnits(t int, u float64) float64 {
-	switch t {
+	return pointsToUnits(defaultUnitConfig{Unit: t}, u)
+}
+
+func pointsToUnits(unitCfg unitConfigurator, u float64) float64 {
+	if unitCfg.getConversionForUnit() != 0 {
+		return u * unitCfg.getConversionForUnit()
+	}
+	switch unitCfg.getUnit() {
 	case UnitPT:
 		return u / conversionUnitPT
 	case UnitMM:
@@ -83,14 +112,39 @@ func PointsToUnits(t int, u float64) float64 {
 
 // UnitsToPointsVar converts units of the provided type to points for all variables supplied
 func UnitsToPointsVar(t int, u ...*float64) {
+	unitsToPointsVar(defaultUnitConfig{Unit: t}, u...)
+}
+
+func unitsToPointsVar(unitCfg unitConfigurator, u ...*float64) {
 	for x := 0; x < len(u); x++ {
-		*u[x] = UnitsToPoints(t, *u[x])
+		*u[x] = unitsToPoints(unitCfg, *u[x])
 	}
 }
 
 // PointsToUnitsVar converts points to the provided units for all variables supplied
 func PointsToUnitsVar(t int, u ...*float64) {
+	pointsToUnitsVar(defaultUnitConfig{Unit: t}, u...)
+}
+
+func pointsToUnitsVar(unitCfg unitConfigurator, u ...*float64) {
 	for x := 0; x < len(u); x++ {
-		*u[x] = PointsToUnits(t, *u[x])
+		*u[x] = pointsToUnits(unitCfg, *u[x])
 	}
 }
+
+type unitConfigurator interface {
+	getUnit() int
+	getConversionForUnit() float64
+}
+
+type defaultUnitConfig struct {
+	Unit              int
+	ConversionForUnit float64
+}
+
+func (d defaultUnitConfig) getUnit() int {
+	return d.Unit
+}
+func (d defaultUnitConfig) getConversionForUnit() float64 {
+	return d.ConversionForUnit
+}
diff --git a/gopdf.go b/gopdf.go
index c4ddcd3..62d92e3 100644
--- a/gopdf.go
+++ b/gopdf.go
@@ -1735,7 +1735,7 @@ func (gp *GoPdf) MeasureTextWidth(text string) (float64, error) {
 	if err != nil {
 		return 0, err
 	}
-	return PointsToUnits(gp.config.Unit, textWidthPdfUnit), nil
+	return pointsToUnits(gp.config, textWidthPdfUnit), nil
 }
 
 // MeasureCellHeightByText : measure Height of cell by text (use current font)
@@ -1750,7 +1750,7 @@ func (gp *GoPdf) MeasureCellHeightByText(text string) (float64, error) {
 	if err != nil {
 		return 0, err
 	}
-	return PointsToUnits(gp.config.Unit, cellHeightPdfUnit), nil
+	return pointsToUnits(gp.config, cellHeightPdfUnit), nil
 }
 
 // Curve Draws a Bézier curve (the Bézier curve is tangent to the line between the control points at either end of the curve)
@@ -1969,8 +1969,8 @@ func (gp *GoPdf) init(importer ...*gofpdi.Importer) {
 	gp.compressLevel = zlib.DefaultCompression
 
 	// change the unit type
-	gp.config.PageSize = *gp.config.PageSize.UnitsToPoints(gp.config.Unit)
-	gp.config.TrimBox = *gp.config.TrimBox.UnitsToPoints(gp.config.Unit)
+	gp.config.PageSize = *gp.config.PageSize.unitsToPoints(gp.config)
+	gp.config.TrimBox = *gp.config.TrimBox.unitsToPoints(gp.config)
 
 	// init gofpdi free pdf document importer
 	gp.fpdi = importerOrDefault(importer...)
@@ -1991,22 +1991,22 @@ func (gp *GoPdf) resetCurrXY() {
 
 // UnitsToPoints converts the units to the documents unit type
 func (gp *GoPdf) UnitsToPoints(u float64) float64 {
-	return UnitsToPoints(gp.config.Unit, u)
+	return unitsToPoints(gp.config, u)
 }
 
 // UnitsToPointsVar converts the units to the documents unit type for all variables passed in
 func (gp *GoPdf) UnitsToPointsVar(u ...*float64) {
-	UnitsToPointsVar(gp.config.Unit, u...)
+	unitsToPointsVar(gp.config, u...)
 }
 
 // PointsToUnits converts the points to the documents unit type
 func (gp *GoPdf) PointsToUnits(u float64) float64 {
-	return PointsToUnits(gp.config.Unit, u)
+	return pointsToUnits(gp.config, u)
 }
 
 // PointsToUnitsVar converts the points to the documents unit type for all variables passed in
 func (gp *GoPdf) PointsToUnitsVar(u ...*float64) {
-	PointsToUnitsVar(gp.config.Unit, u...)
+	pointsToUnitsVar(gp.config, u...)
 }
 
 func (gp *GoPdf) isUseProtection() bool {
diff --git a/page_sizes.go b/page_sizes.go
index e501402..d43ef16 100644
--- a/page_sizes.go
+++ b/page_sizes.go
@@ -1,64 +1,64 @@
 package gopdf
 
 // PageSizeLetter page format
-var PageSizeLetter = &Rect{W: 612, H: 792, unitOverride: UnitPT}
+var PageSizeLetter = &Rect{W: 612, H: 792, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeLetterSmall page format
-var PageSizeLetterSmall = &Rect{W: 612, H: 792, unitOverride: UnitPT}
+var PageSizeLetterSmall = &Rect{W: 612, H: 792, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeTabloid page format
-var PageSizeTabloid = &Rect{W: 792, H: 1224, unitOverride: UnitPT}
+var PageSizeTabloid = &Rect{W: 792, H: 1224, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeLedger page format
-var PageSizeLedger = &Rect{W: 1224, H: 792, unitOverride: UnitPT}
+var PageSizeLedger = &Rect{W: 1224, H: 792, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeLegal page format
-var PageSizeLegal = &Rect{W: 612, H: 1008, unitOverride: UnitPT}
+var PageSizeLegal = &Rect{W: 612, H: 1008, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeStatement page format
-var PageSizeStatement = &Rect{W: 396, H: 612, unitOverride: UnitPT}
+var PageSizeStatement = &Rect{W: 396, H: 612, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeExecutive page format
-var PageSizeExecutive = &Rect{W: 540, H: 720, unitOverride: UnitPT}
+var PageSizeExecutive = &Rect{W: 540, H: 720, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA0 page format
-var PageSizeA0 = &Rect{W: 2384, H: 3371, unitOverride: UnitPT}
+var PageSizeA0 = &Rect{W: 2384, H: 3371, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA1 page format
-var PageSizeA1 = &Rect{W: 1685, H: 2384, unitOverride: UnitPT}
+var PageSizeA1 = &Rect{W: 1685, H: 2384, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA2 page format
-var PageSizeA2 = &Rect{W: 1190, H: 1684, unitOverride: UnitPT}
+var PageSizeA2 = &Rect{W: 1190, H: 1684, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA3 page format
-var PageSizeA3 = &Rect{W: 842, H: 1190, unitOverride: UnitPT}
+var PageSizeA3 = &Rect{W: 842, H: 1190, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA4 page format
-var PageSizeA4 = &Rect{W: 595, H: 842, unitOverride: UnitPT}
+var PageSizeA4 = &Rect{W: 595, H: 842, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA4Landscape page format
-var PageSizeA4Landscape = &Rect{W: 842, H: 595, unitOverride: UnitPT}
+var PageSizeA4Landscape = &Rect{W: 842, H: 595, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA4Small page format
-var PageSizeA4Small = &Rect{W: 595, H: 842, unitOverride: UnitPT}
+var PageSizeA4Small = &Rect{W: 595, H: 842, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeA5 page format
-var PageSizeA5 = &Rect{W: 420, H: 595, unitOverride: UnitPT}
+var PageSizeA5 = &Rect{W: 420, H: 595, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeB4 page format
-var PageSizeB4 = &Rect{W: 729, H: 1032, unitOverride: UnitPT}
+var PageSizeB4 = &Rect{W: 729, H: 1032, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeB5 page format
-var PageSizeB5 = &Rect{W: 516, H: 729, unitOverride: UnitPT}
+var PageSizeB5 = &Rect{W: 516, H: 729, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeFolio page format
-var PageSizeFolio = &Rect{W: 612, H: 936, unitOverride: UnitPT}
+var PageSizeFolio = &Rect{W: 612, H: 936, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSizeQuarto page format
-var PageSizeQuarto = &Rect{W: 610, H: 780, unitOverride: UnitPT}
+var PageSizeQuarto = &Rect{W: 610, H: 780, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // PageSize10x14 page format
-var PageSize10x14 = &Rect{W: 720, H: 1008, unitOverride: UnitPT}
+var PageSize10x14 = &Rect{W: 720, H: 1008, unitOverride: defaultUnitConfig{Unit: UnitPT}}
 
 // // PageSizeEnvelope page format
 // var PageSizeEnvelope	= Rect{W:???,H:???}
diff --git a/rect.go b/rect.go
index 2eeeb36..727bb32 100644
--- a/rect.go
+++ b/rect.go
@@ -4,7 +4,7 @@ package gopdf
 type Rect struct {
 	W            float64
 	H            float64
-	unitOverride int
+	unitOverride defaultUnitConfig
 }
 
 // PointsToUnits converts the rectangles width and height to Units. When this is called it is assumed the values of the rectangle are in Points
@@ -13,12 +13,13 @@ func (rect *Rect) PointsToUnits(t int) (r *Rect) {
 		return
 	}
 
-	if rect.unitOverride != UnitUnset {
-		t = rect.unitOverride
+	unitCfg := defaultUnitConfig{Unit: t}
+	if rect.unitOverride.getUnit() != UnitUnset {
+		unitCfg = rect.unitOverride
 	}
 
 	r = &Rect{W: rect.W, H: rect.H}
-	PointsToUnitsVar(t, &r.W, &r.H)
+	pointsToUnitsVar(unitCfg, &r.W, &r.H)
 	return
 }
 
@@ -28,11 +29,24 @@ func (rect *Rect) UnitsToPoints(t int) (r *Rect) {
 		return
 	}
 
-	if rect.unitOverride != UnitUnset {
-		t = rect.unitOverride
+	unitCfg := defaultUnitConfig{Unit: t}
+	if rect.unitOverride.getUnit() != UnitUnset {
+		unitCfg = rect.unitOverride
 	}
 
 	r = &Rect{W: rect.W, H: rect.H}
-	UnitsToPointsVar(t, &r.W, &r.H)
+	unitsToPointsVar(unitCfg, &r.W, &r.H)
+	return
+}
+
+func (rect *Rect) unitsToPoints(unitCfg unitConfigurator) (r *Rect) {
+	if rect == nil {
+		return
+	}
+	if rect.unitOverride.getUnit() != UnitUnset {
+		unitCfg = rect.unitOverride
+	}
+	r = &Rect{W: rect.W, H: rect.H}
+	unitsToPointsVar(unitCfg, &r.W, &r.H)
 	return
 }