Subject to the completion of paperwork, Porter will be available for Saturday's game against Morecambe and can also be selected for Tuesday's trip to Mansfield Town in the Johnstone's Paint Trophy.
Speaking about the loan deal, Spireites chief executive Chris Turner said: "As we're currently suffering from a mini injury crisis amongst the club's strikers and with Eoin Doyle's partner being in the late stages of her pregnancy, we called around the local clubs for cover in that position.
"Chris [Porter] was first on our list and Sheffield United have been extremely helpful in getting the deal sorted by this afternoon," added Turner.
The Wigan-born striker began his professional career at Bury, before enjoying spells at Oldham Athletic, Motherwell and Derby. He has scored 12 goals in 37 starts during his time at Bramall lane.