An organisation that advocates alternatives to jail says a new tool reveals the thousands of dollars per day that imprisonment costs local communities.

The justice reinvestment calculator, released by Just Reinvest New South Wales, shows adult and juvenile incarceration and community supervision costs $2.5 million per day across the state.

The calculator is designed to break down the cost of imprisoning inmates from each postcode.

For example, the combined cost of incarceration and community supervision of offenders from Broken Hill in the state's far west is around $10,000 per day, while for the Riverina city of Wagga Wagga, that figure is around $23,000.

Just Reinvest chair Sarah Hopkins said the tool highlighted the money that could be saved and reinvested in alternative ways to deal with offenders, and prevent crime.

"What we know is that we have been approached by a number of communities who are telling us that not enough money is being spent where it's most needed, in areas around keeping kids at school, finding jobs for school leavers, better health solutions for young people," Ms Hopkins said.

She argued money spent on keeping an offender in prison would be better invested in the community to prevent the crime happening in the first place.

"Of course we're not suggesting that it's going to be as simple as shifting that [money] straight into the community," she said.

"But it just raises the question around once you put all those figures together, there is a way to start talking to government, raising with government ways that it could be reinvested back into the community."

The figures are drawn from a range of sources, including the Australian Bureau of Statistics, whereas the cost of incarceration is calculated based on a study by the Australian National Council on Drugs.