If it is unpaid leave (such as FMLA leave, or if you are letting them take unpaid leave voluntarily), then you simply divide the number of work days they work by the number of work days they are out that month and multiply by the salary. E.g. someone earns $60k/year, or $5k per month; they are out for 12 of 24 work days, or 50% of the time; they get $2,500.If they are getting paid leave, they get their normal monthly salary but typically do not accrue additional sick or vacation days while on leave.