South Australia's seven-day lockdown in July, prompted by an outbreak of COVID-19 cases, cost the state up to $446 million, Business SA says.
The group surveyed its members and found that losses ranged from about $10,000 for those involved in recreational services to about $45,000 for employers in the construction sector.
It said government support provided during the lockdown was welcome but the results of the survey showed the harsh reality of unrecoverable losses.
"These numbers are the first true indication of business losses resulting from a South Australian lockdown, and also the associated human impact," chief executive Martin Haese said.
"It's important to note that although the lockdown lasted for only seven days, the financial implications of associated restrictions that remain in place continue to have a detrimental effect on businesses and the economy at large."
The survey also found 40 per cent of businesses believed they would not recover any of their losses while only four per cent expected to fully recover the missed trade.
Business SA said it was not arguing that the lockdown should not have happened but was asking governments consider the financial impact on businesses when determining future support packages.