Financial impact of nurses ballot question? Depends who’s counting.

Supporters and opponents of Question 1 are offering wildly different figures on what the cost would be to hospitals.Pat Greenhouse/Globe Staff/File

When they talk about the impact of ballot Question 1, Massachusetts hospital executives keep repeating one big number: $1 billion. That’s how they’ve described the approximate cost — annually — of the question that seeks to regulate nurse staffing.

Last week, they started detailing the costs for individual hospitals. If the ballot question passes, the parent company of Cape Cod Hospital estimates it would have to spend more than $34 million a year to comply with the measure. The parent of South Shore Hospital would spend more than $33 million. Boston Medical Center and Baystate Medical Center each would spend about $28 million.

Among hospital systems, Partners HealthCare, the state’s largest, estimates it would have to spend $140 million across its facilities. Southcoast Health pegged its costs at $38 million.

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Several other hospitals also released estimates in the millions. You get the idea.

Question 1 would set limits for the number of patients assigned to hospital nurses. The Massachusetts Nurses Association, a labor union, is promoting the question, arguing that such limits would allow nurses to provide safer care to patients.

Hospital leaders, however, say the measure would be “devastating.” They say it would strip them of the flexibility they need to respond to patient needs in real time.

“Question 1 is fraught with unintended consequences that would significantly threaten patient care here at BMC,” Nancy Gaden, chief nursing officer at Boston Medical Center, said in a news release. “Mandated staffing ratios will . . . negatively impact both patient safety and the ability of our hospital to offer live-saving care to people across the region.”

Unsurprisingly, the nurses union disputes the hospital industry numbers. A union-backed study put the total costs of the ballot question at about $47 million — for all Massachusetts hospitals.

“Hospital executives have continued to throw out inflated, unrealistic numbers in the interest of scaring the voters,” said Kate Norton, a spokeswoman for the nurses union.