diff --git a/README.md b/README.md
index c66b574..e3c4e0a 100644
--- a/README.md
+++ b/README.md
@@ -34,12 +34,12 @@ $ aspect-ratio
     $ aspect-ratio <width><height>[options]
 
     options:
-  	 -s	     specified a separator. (by default is ':').
-  	 --version   output the current version.
+     -s          specified a separator. (by default is ':').
+     --version   output the current version.
 
     examples:
-  	 aspect-ratio 1920 1080
-  	 aspect-ratio 800 600 -s /
+     aspect-ratio 1920 1080
+     aspect-ratio 800 600 -s /
 ```
 
 ## License
diff --git a/bin/index.js b/bin/index.js
index 7bed8b8..18679f4 100755
--- a/bin/index.js
+++ b/bin/index.js
@@ -5,7 +5,7 @@ const cli = require('meow')({
   pkg: '../package.json',
   help: [
     'Usage',
-    '  $ aspect-ratio <width><height>[options]',
+    '  $ aspect-ratio <width> <height> [options]',
     '\n  options:',
     "\t -s\t     specified a separator. (by default is ':').",
     '\t --version   output the current version.',
diff --git a/src/index.js b/src/index.js
index 1d92c08..5df3b16 100644
--- a/src/index.js
+++ b/src/index.js
@@ -2,7 +2,7 @@
 
 const { gcd, highestFirst, formatAspectRatio } = require('./util')
 
-module.exports = (height, width, seperator = ':') => {
+module.exports = (width, height, seperator = ':') => {
   if (typeof height !== 'number') {
     throw new Error(
       `Invalid height: expected a \`number\`, received \`${height}\``
@@ -17,5 +17,5 @@ module.exports = (height, width, seperator = ':') => {
 
   const [h, w] = highestFirst(height, width)
   const divisor = gcd(h, w)
-  return formatAspectRatio(h, w, divisor, seperator)
+  return formatAspectRatio(width, height, divisor, seperator)
 }
diff --git a/test/index.js b/test/index.js
index 85b8662..7018f5f 100644
--- a/test/index.js
+++ b/test/index.js
@@ -5,8 +5,13 @@ const should = require('should')
 
 describe('aspect ratio', () => {
   it('1024x768', () => should(aspectRatio(1024, 768)).equal('4:3'))
+  it('768x1024', () => should(aspectRatio(768, 1024)).equal('3:4'))
   it('1920x1080', () => should(aspectRatio(1920, 1080)).equal('16:9'))
   it('1280x1024', () => should(aspectRatio(1280, 1024)).equal('5:4'))
+  it('1024x1280', () => should(aspectRatio(1024, 1280)).equal('4:5'))
+  it('1080x1920', () => should(aspectRatio(1080, 1920)).equal('9:16'))
+  it('3840x2160', () => should(aspectRatio(3840, 2160)).equal('16:9'))
+  it('2160x3840', () => should(aspectRatio(2160, 3840)).equal('9:16'))
   it('specifying output separator', () =>
     should(aspectRatio(1920, 1080, '/')).equal('16/9'))