Think of your smartphone screen as a windscreen on a vehicle. Sometimes, through their service life, it may cop a stone or a fall causing it to crack or shatter.
The toughened glass used on a mobile phone provides protection with resistance to cracking, but when it does crack, it usually shatters. There are a number of layers to a smartphone screen, from the bottom Liquid Crystal Display (LCD) is topped by glass substrates and covers, driving and sensing capacitive grids and numerous bonding layers.
In most cases the shattered smartphone screen will be difficult to read but will still work. But be careful, as occasionally shards of glass can come loose. Clear contact or wide strips of transparent tape will prevent shards coming loose as an emergency stop-gap until the screen can be repaired.
REPAIR
There are a few options when it comes to replacing a smartphone screen with the cost varying significantly.
The first, and least palatable, is to do it yourself if you can get the parts. In most cases this is only available for popular phones like iPhones and Samsung S7. Repair kits with non-genuine screens complete with tools can be found on sites like eBay and cost around $50 for an iPhone 5C, $70 for an iPhone 6 or 6s, $115 for an iPhone 7 and $180 for a Samsung S7.
But be warned, unless blessed with dexterity and experience, it is not a simple task and beside voiding any warranty, it's easy to cause further damage.
NON-AUTHORISED REPAIRERS
If planning on using a cheaper non-genuine replacement screen, it may be better to have an experienced technician carry out the repairs. The additional cost is not significant, and the repair shop will have access to screens for less popular phones like the T84 Telstra Tough Max and repair time is around two hours.
Repair prices will vary between individual shops but as a guide, expect to pay:
AUTHORISED REPAIRERS
It may also be worth looking at getting a genuine repair done on later model Apple handsets as the cost difference is not significant, any remaining warranty will be kept and non-genuine screens can be inferior quality.
Genuine iPhone screen replacements can be arranged with an "appointment" at an Apple store for repair, or booked to be posted in for repairs. Both can be arranged through an online system on the Apple website requiring the handset serial number. Costs through Apple at the time of printing is $209 regardless of the model. In store, the repair takes around 3-4 hours. Posted turnaround time is around 10-days total provided nothing else is damaged.
Apple care plus is an additional warranty which can be purchased within 60-days of handset purchase for around $189 and entitles the owner up to two screen replacements costing $45 or $149 for any other damage. If you are tough on phones this may be worth considering but a quality case may be better insurance.