A federal judge has rejected Lyft Inc.’s proposed $12.25 million settlement to resolve a case filed by California drivers over their status as independent contractors of the ride-hailing service.In a ruling Thursday, Judge Vince Chabria of California’s Northern District said the settlement amount shortchanged drivers’ mileage expenses by at least half. The plaintiffs’ lawyers had originally estimated the value of reimbursement at $64 million, but the judge said the figure could be as high as $126 million after a further calculation based on updated data from Lyft.

“We believe we reached a fair agreement with the plaintiffs and are currently evaluating our next steps,” a Lyft spokesman said.

Under the settlement, Lyft would have avoided changes to a labor model that relies on classifying drivers as independent contractors. The drivers had sought to be reclassified as employees, which would have made them eligible for overtime pay, minimum wage and other benefits.

The settlement would have only required Lyft to make the payment and agree not to terminate drivers at will, while also giving drivers notice if they are in danger of being pulled off the system.

Judge Chabria said the parties could file a revised settlement proposal by the end of May.

“As the court recognized, we had been working from older data that Lyft had provided to us,” Shannon Liss-Riordan, the attorney representing the drivers, said in an emailed statement. “We look forward to revisiting this now that Lyft has provided us more updated data, or pressing forward if a new resolution cannot be reached.”

Ms. Liss-Riordan has also brought class-action suits against Uber Technologies Inc. with similar allegations that drivers should be regarded as employees rather than contractors. That case is proceeding in California federal court with a trial date set for June.