What this calculator does
Mid-run you have one useful question: at this rate, where do I finish? That is a subtraction and an addition, but doing it in your head while playing is exactly when you get it wrong. Enter the clock at a checkpoint and the split you are chasing, and this gives you the delta and the projected finish.
The projection assumes the rest of the run matches the comparison run, so it is a straight carry-forward of your current delta rather than a prediction. That is the same assumption the pace display in a timer makes, and it is honest as long as you remember the back half of a run is usually where the variance lives.
The formula
The delta is your elapsed time minus the split you are comparing against. Negative means ahead. The projected finish is the target finish time plus that delta, which assumes you neither gain nor lose further time. All three fields are in seconds, and the results are shown as a clock, so a run of an hour is entered as 3600 and comes back as 1:00:00.
| Term | Meaning |
|---|---|
| Elapsed | What your timer reads at the checkpoint. |
| Target split | What the run you are chasing read at that same checkpoint. |
| Delta | The difference. Negative is ahead of pace. |
| Projected finish | Target finish plus the delta. |
The inputs explained
| Field | What to enter |
|---|---|
| Elapsed at the checkpoint (s) | Your current time at the checkpoint, in seconds. 12 minutes 22 seconds is 742. |
| Target split at that point (s) | The comparison run time at the same checkpoint, in seconds. This is usually your personal best or a goal pace. |
| Target finish time (s) | The finish time of the run you are comparing against, in seconds. An hour is 3600. |
When to use it
Checking pace against a personal best
Use your PB split and your PB finish time. The projected finish then tells you what you beat the PB by if the rest of the run holds.
Chasing a round number
Set the target finish to the barrier you want, such as 1800 for a 30 minute run, and set the split to what that pace needs at your checkpoint. The delta then reads as time in hand rather than time against a previous run.
Deciding whether to reset
Early deltas are noisy and a few seconds lost in the first minutes usually mean little. The share-of-run figure tells you how much of the run is still ahead, which is the context that makes a delta worth acting on.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What does being a few seconds up at a checkpoint mean at the finish?
Only the elapsed time changes. The projection carries the gap straight through.
| Elapsed at checkpoint | Projected finish | Ahead or behind |
|---|---|---|
| 700 s | 58:55 | ahead by 1:05 |
| 730 s | 59:25 | ahead by 0:35 |
| 742 s | 59:37 | ahead by 0:23 |
| 765 s | 1:00:00 | level, 0:00 |
| 790 s | 1:00:25 | behind by 0:25 |
| 840 s | 1:01:15 | behind by 1:15 |
Questions
Why are the inputs in seconds?
So that one number per field is enough and there is nothing to parse. Multiply minutes by 60 and add the seconds: 12:22 is 12 × 60 + 22 = 742. The results come back formatted as a clock.
Does it account for the rest of the run being harder?
No. It carries your current delta forward unchanged. If the back half is where you usually lose time, treat the projection as a best case.
Can I use it for sum of best?
Not directly. This compares one checkpoint against one comparison run. Sum of best needs every individual segment best, which is a different calculation.
What counts as a checkpoint?
Anything you have a reliable comparison time for. The more often you check, the more noise you see, so most runners use a handful of meaningful splits rather than every room.
If you are grinding levels rather than racing a clock, XP to next level turns an XP rate into time, and FPS to frame time covers the other kind of timing that matters in a run.