The move is a key plank in their strategy to encourage UK consumers to see South African produce as the 'second local' option first choice when UK fruit and veg are not in season.
Early indications showed South African fruit could be grown, refrigerated and shipped to the UK on "at least a carbon-neutral basis", said Anton Rabe, executive director of the Hortgro association.
The calculator and the methodology behind it had been reviewed by the Carbon Trust, and a claim to carbon neutrality could ultimately be a powerful tool in overcoming "misconceptions", he added.
"There are a small number of consumers who won't buy South African fruit because of the food miles," said Rabe.
Consumer research had also shown UK shoppers often perceived South African produce as 'out of season', he added, "even though there is, of course, a season for everything".
The calculator, developed jointly by the fruit growing and viniculture industries, takes into account the positive effect of growing fruit in the first place in that it removes carbon from the atmosphere.
The calculator has already attracted the interest of other southern hemisphere countries, including Australia and New Zealand.
The South African stone and top fruit industries this week announced details of their new winter campaign, which will involve on-pack promotions with two retailers, outdoor ads and in-store sampling.