There are no doubts that website loan speed leads to better and higher conversion. Visitor will often leave a website if it is too slow thus increasing your bounce rate. As a rule of thumb, It is best to have a page that loads under 5 seconds. Page speed is also a factor for SEO.
You can use the link below from Google to test for your website speed.
Specifically catered for mobile device load speed test
The above link will show you factors that effect yours wordpress speed. It is best to use both of the tools to fine tune your WordPress.
Why Google ? We would definitely try to stick with Google tools as Google will possibly use the same technology for their search engine rankings and other products.
For a start , hosting is the most important factor that will influence your website loading time. Having the budget for VPS and better hosting would definitely help however most of us would probably be stucked with our shared hosting for years due to limited budget. Some services worth mentioning are WPEngine but they are quite expansive. These hosting are highly specialized in hosting WordPress software. Do expect to pay a starting price from $30 monthly for a single domain. If you have limited budget you can follow the steps below to reduce your load speed. We managed to scrap 10 seconds off some of our websites and doubled the conversion
Minimize Post load
Go to setting , Reading -> Blog pages show at most and minimize the number of posts that you are showing when loading your main WordPress website. There are huge loading time difference if you are only loading 1 posts versus loading 10 posts at loading time
Remove Social sharing button
Do not use too much social sharing button. These plugins do slow down your load time especially if you are using cheap shared hosting.
This would be the most important factor that effects your load speed besides hosting. Believe it or not, some inefficient themes take a few extra seconds to load. Always have a light and toned down Theme if you want to achieve faster load speed especially if you are using budget hosting. Generally the default themes from WordPress.org are good enough for load speed. Use the test tools to consider your theme choice.
This would be the main page where visitor first visits your website. Strip down unnecessary fancy flashing items. Avoid having a high resolution image or fancy video on the loading page as this will increase the load time dramatically.
Cache Plugin plays an important role that may speed your website by a few seconds. There are generally pretty good free WordPress cache plugin such as W3 Total Cache and WP Super Cache . After some testing, we would recommend WP Fastest Cache and we find this works faster on our websites
Content Delivery Network (CDN )
Having a CDN definitely helps as some of your files will be loaded directly from other places. Most of WordPress Cache plugins support some sort of free CDN. You will just need to enable it. You can also consider Cloudflare which do offers free account for some serious CDN however this would involve some Domain Name and DNS tweaking.
Having high resolution photos may make your website more attractive however it could unknowingly add more loading time to your website. Having a high resolution image in front of your wesbite is a bad idea especially if you are using shared hosting. WP Smush is a great WordPress Plugin to optimized all your uploaded images.
Webmaster should regularly optimize their and update to the latest WordPress version. Deactivate and remove unused plugins. Draft and unwanted posts to be removed. Database gets cluttered with unwanted data especially when it is very old WordPress. and this may cause inefficiency when loading. WP-Optimize is a good plugin to help webmaster with this.
Software and Hardware resources
While this option is limited based on hosting, we can only do what is best on our side. These is usually done from your Cpanel using php.ini depending on your hosting. Use the highest memory limit allowed for your WordPress. Opt for the latest software from your hosting whenever possible. . Having PHP7 can dramatically increase your WordPress speed.