diff --git a/data/data.go b/data/data.go
index 2fab83a..8575028 100644
--- a/data/data.go
+++ b/data/data.go
@@ -12,8 +12,8 @@ import (
 // Options specifies transformations that can be performed on a
 // requested image.
 type Options struct {
-	Width  int // requested width, in pixels
-	Height int // requested height, in pixels
+	Width  float64 // requested width, in pixels
+	Height float64 // requested height, in pixels
 
 	// If true, resize the image to fit in the specified dimensions.  Image
 	// will not be cropped, and aspect ratio will be maintained.
@@ -21,7 +21,7 @@ type Options struct {
 }
 
 func (o Options) String() string {
-	return fmt.Sprintf("%dx%d", o.Width, o.Height)
+	return fmt.Sprintf("%vx%v", o.Width, o.Height)
 }
 
 func ParseOptions(str string) *Options {
@@ -40,10 +40,10 @@ func ParseOptions(str string) *Options {
 	}
 
 	if w != "" {
-		o.Width, _ = strconv.Atoi(w)
+		o.Width, _ = strconv.ParseFloat(w, 64)
 	}
 	if h != "" {
-		o.Height, _ = strconv.Atoi(h)
+		o.Height, _ = strconv.ParseFloat(h, 64)
 	}
 
 	for _, part := range parts[1:] {
diff --git a/proxy/proxy.go b/proxy/proxy.go
index 3686be7..b72a404 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -91,11 +91,11 @@ func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if p.MaxWidth > 0 && req.Options.Width > p.MaxWidth {
-		req.Options.Width = p.MaxWidth
+	if p.MaxWidth > 0 && int(req.Options.Width) > p.MaxWidth {
+		req.Options.Width = float64(p.MaxWidth)
 	}
-	if p.MaxHeight > 0 && req.Options.Height > p.MaxHeight {
-		req.Options.Height = p.MaxHeight
+	if p.MaxHeight > 0 && int(req.Options.Height) > p.MaxHeight {
+		req.Options.Height = float64(p.MaxHeight)
 	}
 
 	u := req.URL.String()
diff --git a/proxy/proxy_test.go b/proxy/proxy_test.go
index d23f872..85d7f83 100644
--- a/proxy/proxy_test.go
+++ b/proxy/proxy_test.go
@@ -88,6 +88,10 @@ func TestNewRequest(t *testing.T) {
 			"http://localhost/1x2,fit/http://example.com/",
 			"http://example.com/", &data.Options{1, 2, true}, false,
 		},
+		{
+			"http://localhost/0.1x0.2,fit/http://example.com/",
+			"http://example.com/", &data.Options{0.1, 0.2, true}, false,
+		},
 	}
 
 	for i, tt := range tests {
diff --git a/transform/transform.go b/transform/transform.go
index ef0e891..6a24c6a 100644
--- a/transform/transform.go
+++ b/transform/transform.go
@@ -35,14 +35,26 @@ func Transform(img data.Image, opt *data.Options) (*data.Image, error) {
 		return nil, err
 	}
 
+	var h, w int
+	if opt.Width > 0 && opt.Width < 1 {
+		w = int(float64(m.Bounds().Max.X-m.Bounds().Min.X) * opt.Width)
+	} else {
+		w = int(opt.Width)
+	}
+	if opt.Height > 0 && opt.Height < 1 {
+		h = int(float64(m.Bounds().Max.Y-m.Bounds().Min.Y) * opt.Height)
+	} else {
+		h = int(opt.Height)
+	}
+
 	// resize
 	if opt.Fit {
-		m = imaging.Fit(m, opt.Width, opt.Height, imaging.Lanczos)
+		m = imaging.Fit(m, w, h, imaging.Lanczos)
 	} else {
 		if opt.Width == 0 || opt.Height == 0 {
-			m = imaging.Resize(m, opt.Width, opt.Height, imaging.Lanczos)
+			m = imaging.Resize(m, w, h, imaging.Lanczos)
 		} else {
-			m = imaging.Thumbnail(m, opt.Width, opt.Height, imaging.Lanczos)
+			m = imaging.Thumbnail(m, w, h, imaging.Lanczos)
 		}
 	}