It is the largest number of deaths announced on one day since 30 May, when 14 were also reported.
There have been 1,736 deaths since the start of the pandemic and 38,361 cases.
There were 9,464 tests carried out on Tuesday.
A total of 669,604 people have been tested for coronavirus in Wales, with 631,243 testing negative.
image captionMap showing how many people have died with coronavirus in Wales
Cardiff reported the most cases with 223 positive tests reported on Tuesday, followed by Rhondda Cynon Taf with 140 reported cases.
The Welsh capital also has the highest weekly case rate at 293 cases per 100,000 people, closely followed by Merthyr at 253.6 per 100,000 and Rhondda Cynon Taf at 229.2 per 100,000 people.
Cardiff currently has the highest Covid-19 case rate in Wales
This is how the cases break down in different neighbourhoods pic.twitter.com/vRagvrvObg
— BBC Wales News (@BBCWalesNews) October 21, 2020
Public Health Wales is now publishing more localised data on case rates across Wales on its dashboard.
We can see in Cardiff how case rates can vary across the city, with particular hotpots showing up in the city’s traditional student areas.
This includes m427 cases among Cardiff University students in this period, although it is not the only factor.
Wales will go into a “short, sharp” national lockdown from Friday until Monday 9 November in a bid to reverse the increase in cases.
People will be told to stay at home, while pubs, restaurants and non-essential shops will shut.
- What do the stats tell us about Covid-19 in Wales?
- Q&A: What can you do in Wales-wide lockdown?
image captionMap showing weekly case rates across Wales
PHW’s figures mostly involve hospital deaths and only include cases when the virus has been confirmed in a laboratory test.
The figures do not include deaths of residents from Powys in hospitals in England, although these are included in Office for National Statistics data.