Long Rest: resume after an interruption with added time

SRD 5.2.1 · Rest

At the table

1. Start with at least 1 Hit Point; allow at least 8 hours, including 6 hours of sleep and at most 2 hours of light activity.
2. Initiative, a non-cantrip spell, damage or an hour of exertion interrupts the rest.
3. It can resume immediately, adding one hour per interruption; at least an hour rested before interruption grants Short Rest benefits.

Example decision

A creature’s otherwise valid Long Rest is interrupted once by rolling Initiative. It immediately resumes afterward and no other interruption occurs. What extra time does the resume rule require?

One additional hour to finish the rest.

Rolling Initiative is explicitly an interruption. Immediate resumption adds one hour for that interruption, while the other requirements must still be satisfied. Completion restores lost Hit Points and spent Hit Point Dice, restores reduced ability scores and Hit Point maximum, and reduces Exhaustion by one level. Feature recovery follows each feature’s wording.

Watch for this mistake

Do not reuse another edition’s rule about an hour of combat before interruption. Here rolling Initiative itself is listed. After finishing, wait at least 16 hours before starting another Long Rest.

Ask the table

What interrupted the rest, how long had it progressed, and how much time is needed after resuming?

Source rule

A Long Rest is a period of extended downtime—at least 8 hours—available to any creature. During a Long Rest, you sleep for at least 6 hours and perform no more than 2 hours of light activity, such as reading, talking, eating, or standing watch. During sleep, you have the Unconscious condition. After you finish a Long Rest, you must wait at least 16 hours before starting another one. Benefits of the Rest. To start a Long Rest, you must have at least 1 Hit Point. When you finish the rest, you gain the following benefits: Regain All HP. You regain all lost Hit Points and all spent Hit Point Dice. If your Hit Point maximum was reduced, it returns to normal. Ability Scores Restored. If any of your ability scores were reduced, they return to normal. Exhaustion Reduced. If you have the Exhaustion condition, its level decreases by 1. Special Feature. Some features are recharged by a Long Rest. If you have such a feature, it recharges in the way specified in its description. Interrupting the Rest. A Long Rest is stopped by the following interruptions: • Rolling Initiative • Casting a spell other than a cantrip • Taking any damage • 1 hour of walking or other physical exertion If you rested at least 1 hour before the interruption, you gain the benefits of a Short Rest. See also “Short Rest.” You can resume a Long Rest immediately after an interruption. If you do so, the rest requires 1 additional hour per interruption to finish.

Source: SRD 5.2.1, 185. Online guide.