Kyle Sandilands announced his engagement to girlfriend Tegan Kynaston on his KIIS FM radio show on Monday.

Tegan's huge diamond engagement ring was designed by upmarket House of K'dor jewellery store in Sydney's Double Bay.

Following the announcement, the luxury jeweller congratulated the couple on their engagement.

'Congratulations @Kyleandjackieo and @Tegankynaston. #SheSaidYes,' they wrote on Instagram.

It comes after another jeweller estimated Kyle had spent at least a million dollars on the design.

Tobias Kormind, managing director of Europe's largest online diamond jeweller, told Daily Mail Australia: 'Tegan's ring is an emerald-cut diamond set on a split shank platinum band.'

'[It would be] worth over $1.14million for a decent quality diamond, at least F colour, VS1 clarity,' he added.

Mr Kormind, who did not make Tegan's ring but has studied photos of the design, noted that a key feature of the ring is the split shank, which is a style featuring a band that separates as it reaches the centre setting.

'Split shank rings are relatively unusual and Beyoncé is one of the few other celebrities to sport a split shank ring, but [Beyoncé's] is an 18-carat emerald-cut diamond,' he said.

'Split shanks rings are very elegant and actually are more secure,' Mr Kormind added.

Kyle would've had no trouble splashing out on Tegan's ring, given he recently valued his business empire at about $100million.

However, he did say on air on Tuesday he didn't spent more than a million dollars.

It comes after Kyle opened up about his extravagant proposal on his first day back on  on Monday.

Kyle explained he'd hired a venue and arranged for fireworks, candles and a lavish meal before getting down on one knee - but admitted not everything went to plan.

The shock jock had organised for singer-songwriter Conrad Sewell to fly in from overseas and perform the couple's favourite song for their proposal.

'But two days before the proposal, Conrad rang me and he was very upset because he had caught Covid,' the KIIS FM host said.