How Mileage Is Calculated

YardPath has no connection to your truck. It never reads your odometer, your speedometer, or your engine, there’s no dongle, no OBD plug, no vehicle integration. Every distance in your log is worked out from your iPhone’s sense of where it has been, or from map data, and every one of them is an estimate.

That’s not a defect to apologize for; it’s how every phone-based mileage app works. But you’re the one signing the return, so you deserve to know exactly how the number was produced and which direction it’s likely to be off.

The short version

• A trip distance is an estimate, and it can land high or low.
• Three different methods are used depending on the trip and your signal, and they have different tendencies.
• Review your trips. Correct anything that looks wrong, and type in the real number when you have one. YardPath marks the trips it has doubts about under Trips to Check, but it can only mark what it noticed, reviewing the rest is still on you.
• What you’re required to track, and how it’s classified, is between you and your tax professional. YardPath is a recordkeeping tool, not tax advice.

Method 1: automatic trips, adding up where your phone has been

This is what runs when you tap a job En Route with tracking on.

Your iPhone reports its position as you drive, at its most precise navigation-grade setting, roughly every 50 feet of movement. YardPath draws a straight line from each position to the next and adds those lines up. String together enough short straight lines and you trace a curving road closely.

Readings the phone isn’t confident about are thrown out rather than trusted. If it rates a fix as worse than about 200 feet of accuracy, that point doesn’t count toward your distance.

Why it can come out short: every straight line cuts the corner a little. A cloverleaf interchange, a switchback, or a winding country road loses a bit on each curve. Worse, if you lose signal entirely, in a tunnel, a parking deck, a deep valley, or under heavy tree cover, the line drawn across that gap is a shortcut compared to the road you actually drove. YardPath keeps track of when more than a minute passes between usable readings.

Why it can come out long: GPS drifts while you’re sitting still. Idling at a long light, waiting at a gate, or parked with the app running, your phone can report small position changes that aren’t real movement. Those fictional feet add up over a day of stops.

Net effect: on ordinary road driving these two errors partly cancel, and the total usually lands within a few percent of true. Dense downtown blocks, tunnels, mountain roads, and heavy canopy are where it strays most.

Method 2: manual trips with a signal, a real road route

When you log a trip by hand and your phone can reach the network, YardPath asks Maps for one driving route between your start and end points and uses that route’s distance. This is genuine road distance, following actual streets, not a straight line.

Why it can differ from what you drove: it’s the route Maps suggests, not the route you took. If you detoured for fuel or supplies, went around a closure, dropped a helper off, or took the shortcut you’ve used for fifteen years, the number reflects Maps’ idea of the trip rather than yours.

You’ll see this one as a plain figure, like 4.2 mi.

Method 3: manual trips without a signal, a straight line

If your phone can’t reach the network, or the route lookup is throttled or takes longer than about ten seconds, YardPath falls back to a direct point-to-point distance, the “as the crow flies” line between the two locations.

This one is systematically short, and it’s the one to watch. A straight line is always shorter than or equal to the road distance, never longer. Roads bend around property lines, rivers need bridges, and the interstate loops around the town instead of through it. A straight-line figure commonly lands 20 to 40 percent under the real driving distance, and on the wrong pair of addresses it can be off by far more.

How to spot it: the distance appears with a ≈ in front of it, like ≈ 4.2 mi, and a small caption reads estimated, no network. Treat that number as a floor, not an answer. Re-enter the trip once you have signal, or type in the real distance. YardPath also captions the trip Straight-line estimate afterward, so you can find it again when you have a better number.

What the labels in your exported log mean

The article so far is about how a distance is computed. Your exported PDF is where it gets reported, and there every trip carries one of three method labels. The cover page of the export spells them out too, so whoever reads it isn’t guessing.

They don’t line up one-to-one with the three methods above, so two notes are worth having.

“Estimated” covers both of the calculated methods. A road route (method 2) and a crow-flies line (method 3) both print as Estimated, because both are figures YardPath produced rather than watched you drive. The app keeps the finer distinction, so open the trip in YardPath when you need to know which one you’re looking at. And a straight-line trip you go back and correct by hand prints Manual instead, whatever it started as.

“Manual” is not a quality mark. It records who supplied the number, not that anyone checked it. YardPath has no way to tell whether you read an odometer, copied a fuel receipt, or estimated from memory, so neither you nor your accountant should read a Manual row as self-certifying. It’s provenance, not verification.

Trips YardPath thinks you should look at

Some trips come out of the process above with a weakness the app can actually detect, and rather than leave you to find them, YardPath collects them in one place: Finances → Mileage → Trips to Check. Each one carries a short caption saying what’s off:

• Spotty GPS, your phone wasn’t confident about its position for much of the trip and a lot of readings got thrown out. These usually come out short.
• Straight-line estimate, there was no network when the trip was logged, so the distance is method 3 above and is almost certainly under the real driving distance.
• Trip didn't finish cleanly, the trip was still recording when the next one started, so it may be missing its last stretch.

Open any trip to type in the real distance, or to say it looks right as recorded. Either way it drops off the list, so the list drains as you work it. You can open any trip this way, not just the marked ones, if you already know one is wrong you don’t have to wait for the app to suspect it.

What that list is not. It surfaces the problems YardPath happened to notice, and nothing more. A trip that isn’t on the list hasn’t been checked, by us or by anyone, it simply didn’t trip one of the three signals above. Every method on this page can be wrong in ways the app has no way to detect, a route you didn’t take, a destination address that’s slightly off, a drive that was personal rather than business. An empty Trips to Check list means nothing obvious was caught, not that the log is right. Reading the log yourself is still the job.

One limit worth knowing about. Only trips logged after this update carry the full detail. Older manual trips can’t be sorted into routed versus straight-line after the fact, that distinction was never written down and it isn’t recoverable, and older automatically-closed trips no longer record that they were GPS-tracked at all. Those trips are labeled as accurately as the app can from what it kept, which means less specifically than a new one.

When YardPath won’t guess at all

If there’s genuinely no drivable route between two addresses, YardPath tells you so instead of quietly substituting a straight line. A crow-flies number for an unroutable destination would look like an answer while being meaningless, so you get an error you can act on rather than a figure you might file.

Your number always wins

When you log a trip by hand, any distance you type in overrides whatever YardPath worked out. If you have an odometer reading, a fuel receipt, or a mapping tool you trust more for that particular drive, use it. Nothing recalculates over the top of a figure you entered yourself.

Getting the most accurate log you can

• Start trips from En Route consistently. A trip recorded live beats one reconstructed later.
• Give the phone a view of the sky. In a metal toolbox, under a seat, or in a center console, it fixes position worse and discards more readings.
• Log manual trips before you lose signal, so you get a road route instead of a straight line.
• Don’t force-quit the app mid-trip.
• Keep customer addresses accurate, since routing starts from the address on the customer record.
• Review the log before you export it. Start with Trips to Check, which gathers the trips YardPath has doubts about, then scan the rest yourself for anything too short for the drive you remember or suspiciously long for a short hop. Tap a trip to correct its distance. See Tracking mileage and Finances & reports.

What this means at tax time

The IRS is interested in your actual business miles and in records that substantiate them. YardPath captures the four fields it asks for on each trip, date, business purpose, destination, and distance, and gets you a log without reconstructing routes from memory in April. What it can’t do is certify that any particular figure is correct, or that your log satisfies any authority.

So: work Finances → Mileage → Trips to Check until it’s empty, then read the rest of the log yourself, correct what’s wrong, keep it honest, and talk to your accountant about what your situation requires. Clearing that list is a starting point, not a sign-off, the trips it never raised are the ones only you can vouch for. If something in the app is producing numbers that look wrong to you, please tell us, that feedback is how this gets better.

The full legal terms covering mileage and location are in section 8 of the Terms of Use.