Four limits govern a property-carrying driver’s day. They run at the same time, and whichever runs out first is the one that stops you.
1. The 11-hour driving limit
After 10 consecutive hours off duty you may drive up to 11 hours. Driving means the vehicle in motion — not loading, fuelling or paperwork.
2. The 14-hour window
You may not drive beyond the 14th consecutive hour after coming on duty. This is the one that catches people out: off-duty time taken during the day does not push the deadline back. A two-hour break inside your shift costs you two hours of window.
3. The 30-minute break
Once you have driven 8 cumulative hours without a 30-minute interruption, a break is required. Any non-driving 30 consecutive minutes satisfies it — off duty, sleeper berth, or on duty not driving.
4. The 60/70-hour cycle
No driving after 60 on-duty hours in 7 consecutive days, or 70 in 8, depending on whether your carrier runs every day. A period of 34 or more consecutive hours off duty restarts the cycle.
Two things that change the picture
Adverse driving conditions may extend both the 11-hour limit and the 14-hour window by up to 2 hours, when conditions you could not have known about beforehand slow you down.
The sleeper berth provision lets the 10-hour off-duty requirement be split, and when a pair qualifies, neither period counts against the 14-hour window.
Source
Summarised from the FMCSA Summary of Hours of Service Regulations. Rules are restated here in our own words — read the original before relying on any of it.