Sub-2 is the goal that gets more half marathon runners than any other, not because it's arbitrary, but because it sits right at the edge of "solid recreational runner" and "actually pretty quick," which means it rewards real training and punishes wishful thinking in equal measure. Here's the actual pace, what it takes to get there, and where most sub-2 attempts quietly fall apart.
5:41 per km, or 9:09 per mile. That's not a rounded-off approximation. Run the numbers yourself with the pace calculator (use the "Sub-2:00 goal" preset) and it lands at exactly 5:41/km for the full 21.0975km. There's no version of this where 5:45/km gets you there with a bit to spare: 5:41/km, held for two hours straight, is the number.
What makes sub-2 harder than it looks on paper is that it has to be held, not just hit for a few km when you're fresh. A 5:41/km pace that feels comfortable at km 3 needs to still feel manageable at km 16, when your legs have a different opinion about "comfortable."
Before you build a training block around this number, find out honestly whether it's within reach this cycle. Take your most recent 10K or half marathon result (a real race or an honest time trial, not a guess) and run it through the race-time predictor. It'll forecast what that fitness level currently supports over 21.1km.
If the predictor puts you within roughly 3-5 minutes of 2:00:00, sub-2 is a legitimate goal for a focused training block. If it puts you 15-20 minutes out, I'd rather be straight with you: that's not a single-cycle jump, no matter how disciplined the next 12 weeks are. That doesn't mean sub-2 is off the table forever. It means this cycle's goal should close part of that gap, not all of it, and the Specific phase should be built around the smaller, achievable target instead of forcing pace work your current fitness can't hold yet.
This is where a lot of sub-2 attempts go wrong before race day even arrives: they train like any other half marathon block (more mileage, a longer long run, done) and skip the part that actually matters for this specific goal. Sub-2 isn't primarily a mileage problem. It's a goal-pace problem. You need to spend real, repeated time at or near 5:41/km, not just accumulate easy kilometers and hope the pace shows up on race day because you're "fit."
Inside the Base → Support → Specific structure I build every plan around, this shows up most in the Specific phase: the weeks closest to race day. That's where tempo runs and goal-pace intervals need to be consistent, not occasional: think sustained blocks at 5:41/km, and tempo efforts that teach your body what that effort actually feels like when you're tired, not just when you're fresh on a Tuesday morning. Base and Support still matter, you can't skip straight to goal-pace work without the aerobic foundation underneath it, but if your Specific phase doesn't include repeated goal-pace exposure, you're training for "a half marathon," not for sub-2 specifically.
The same non-negotiables apply here as in any plan: never two hard days back to back (goal-pace work is a hard day, full stop), at least 2 progression runs across the block so your legs learn to hold pace on tired legs, and speed volume that increases by no more than about 5 minutes a week. Sub-2 doesn't get a pass on those guardrails: if anything, chasing a specific number makes it more tempting to overdo the pace work, and that's exactly how a promising block ends in a strained calf three weeks out.
Even splits are the target. A slight positive split (running a handful of seconds per km slower in the second half than the first) is the realistic outcome even on a well-executed day, because fatigue is real and no amount of good pacing erases it entirely. That's fine. What you're actually protecting against isn't a small positive split, it's a big one.
Practically: your first km should never be your fastest. Race adrenaline, a crowded start corral, and the temptation to "bank time" all push you to go out at 5:25-5:30/km instead of 5:41/km, and it feels easy because you're fresh and excited. It is not free time in the bank. It's a withdrawal you pay back with interest between km 15 and 21, usually in the form of a serious slowdown, not a graceful one. Hold 5:41/km (or even a few seconds slower) through the first 5km on purpose. If you've still got something left at km 16, that's when you're allowed to push.
Going out too fast. This is the big one, by a wide margin. Sub-2 attempts rarely fail because a runner wasn't fit enough on paper. They fail because the first 10km were run 10-15 seconds per km too fast, and the body cashes that cheque somewhere in the last 5km, often costing far more than the seconds gained early on.
Treating goal pace as a race-day surprise. If 5:41/km has never been run in training (really run, in a tempo or goal-pace session, not just glanced at on a watch), race day is the wrong place to find out what it feels like to hold it for two hours.
Under-fueling for a 2-hour effort. Two hours is long enough that fueling and hydration matter, especially in the second half. Skipping this because "it's not a marathon" is a common and avoidable way to lose the last few km.
Chasing the goal before the fitness is there. See the section above: if the race-time predictor says you're 15+ minutes out, forcing sub-2 pace work anyway usually produces injury or a blown-up race, not a breakthrough.
I've run 13 half marathons myself (PB 1:23:45), and sub-2 is one of the goals I coach toward most often. RunLetters Half Marathon Coaching pairs you with a real coach, not an app: someone who builds the goal-pace work into your Specific phase deliberately, and adjusts it as your training actually goes.
See the coaching program5:41 per km, or 9:09 per mile, held for the full 21.0975km. That's the exact number the pace calculator returns when you plug in a 2:00:00 goal. There's no rounding trick that makes it easier, so treat 5:41/km as the number you're training to hold, not a rough target.
Run your most recent honest 10K or half marathon time through the race-time predictor and see what it forecasts for 21.1km. If it puts you within a few minutes of 2:00:00, sub-2 is a realistic training goal for your next block. If it puts you 15-20 minutes away, sub-2 isn't this cycle's goal. That's fine, it just means the Specific-phase pace work should build toward a smaller jump first.
Aim for even splits, and be honest with yourself that a slight positive split (a few seconds per km slower in the second half) is the realistic outcome even on a good day. What you're avoiding isn't a positive split, it's a big one caused by starting too fast. Going out at 5:25/km because the field is fast and adrenaline is high is the single most common way a sub-2 attempt falls apart by km 15.