"Controlling" Lance Hart shot Claire, his wife of 26 years, days after she decided to leave him.
He fired a shotgun at close range at the 50-year-old before pointing the weapon at his 19-year-old daughter Charlotte and pulling the trigger. He then killed himself.
A 12-page note was found on a USB stick in Hart's car in which he explained his actions, the court heard.
Coroner Paul Cooper said the note from Hart, 57, contained the line: "Revenge is dish served cold, karma is a bitch."
Mr Cooper said Hart "knew exactly what he was going to do" when he "murdered" his family on 19 July at the Castle Sports Complex in Spalding, Lincolnshire.
He concluded Claire and Charlotte Hart were unlawfully killed and ruled Hart's death as a suicide.
"It was a single-barrel shotgun, so it was not a question of him just shooting his wife, he then had to unload it, put another cartridge in and shoot it again," said Mr Cooper.
"In my view, this was a cold, calculated, scheming man who went out and deliberately murdered his wife and daughter.
"If he had lived ... he would have been charged with murder. Unfortunately he didn't live to face the consequences of his actions. He took his own life."
Mrs Hart left her home in Moulton, Lincolnshire, on 14 July to move to a new property with the help of her family.
The court heard she was seen by a neighbour loading bags into a car and said: "He'll have a surprise when he gets
home tonight. I've put up with enough for the past 15, 16 years."
The neighbour believed Mrs Hart was joking as "they were always a happy couple together", the court heard.
However, Dale Pateman, who worked with Mrs Hart at a Morrison's store in Spalding, said she had previously spoken of her marital problems.
Detective Inspector Helen Evans said: "Over the last two years, Claire had confided in Dale about problems she was having in her personal relationship with Lance Hart.
"She had described him as being a controlling and selfish man. Claire had told Dale she had become worn out by Lance's behaviour.
"Dale described Claire as beaming and really happy in the few days that had elapsed since leaving her husband."
When Mr Pateman was told the couple would be meeting to exchange documents and photographs, he warned her to be careful, the court heard.
Mrs Evans said: "Claire told him she would be okay as she would have Charlotte with her."
The couple's sons Ryan and Luke said in a statement following the inquest: "Charlotte and our mum were our inspiration and purpose in life.
"They were the two most virtuous and beautiful people we have ever encountered. It is not possible to describe how unfairly and how cruelly they have been taken from us.
"Our world is a darker place because they have gone."