After getting the equaliser before the break, Calvert said the halftime instructions were to be patient and use the corners, where Whanganui were being given plenty of room.
The result was three goals in the first 13 minutes after the resumption.
"We were ruthless going forward," Calvert said.
Captain Vanya Apiata Hodgkinson got a hat trick to take her season tally to eight goals from the team total of 18.
Eva Thompson also scored, while Alice Hetherington came off the bench to add another goal to her season tally.
Calvert said they could have surpassed the scoreline from the previous win in April, but put another couple of shots off to the side.
"However we did say, I'd rather see us going wide, than putting the ball straight at the goalkeeper."
The plan for training now is to work on picking out the runners going into the box.
Whanganui's victory took them to a 2-4-1 season record and vaulted them back up to second on the League table, although well behind Hokowhitu FC, who with a 7-1-0 record have checked out nine points clear of the chasing pack.
Nonetheless, Whanganui managed only one win and draw in each of their previous seasons in the League, meaning they have long since blitzed Calvert's initial target for 2019 in earning more competition points than last year.
"The bigger names within our League are below us at the moment."
He will encourage the side to therefore play with more freedom to see just how well they could do, given Hokowhitu is the only side to beat them in League play this year, in an away game in Palmerston North.
"You just never know."
In the other games, Hokowhitu defeated Taradale AFC away 4-2, while Massey and Palmerston North Marist had a 3-3 draw.
Taradale and Massey are the two League teams left standing in the Federation Cup, and will face each other in the semifinals on June 21, with Moturoa AFC from Taranaki and Gisborne's Riverina AFC in the other playoff.