Zero day set — pace not applied.
Not all miles are created equal. We built a custom terrain index from the PCTA centerline elevation profile, sampled every half mile across the full trail, so your pace automatically adjusts by region — slower through the High Sierra, faster through the flatter Oregon forests — keeping your daily physical effort constant across the entire trail.
What the index does not measure. The terrain index is built from elevation only. It does not account for snow, blowdowns, rock scrambling, exposure, water carries, or trail condition. A low-index zone in a heavy snow year, or a section with a bad blowdown winter, can hike far harder than its number suggests. Treat zone pace as a terrain-shape adjustment, not a difficulty forecast.
On a full terminus-to-terminus plan the Active Index equals the Global Index (1.239). On a shorter route it reflects only the terrain you are actually hiking — which is why a single-zone section hike shows your target pace unchanged. There is no other terrain to trade against.
Few hikers walk their Full Day from the first morning. Trail Legs Ramp-up models your first weeks on trail: you start at a share of your Full Day and build to it in a straight line. It is off until you turn it on in the Pace Engine card.
On the default that is about two days of extra walking: 14 × 30% ÷ 2 = 2.1. Arrival dates round to whole days, so the adds N days line in the card, which is measured on your own plan, can read one more. Starting a section with your trail legs already under you? Leave it off.
The carry row between each resupply stop shows the distance and the hiking time for that segment at your Zone Pace. This is trail time only — it does not include the Stop day at either end, which is why the arrival dates on the cards sit further apart than this number suggests. The colour is set by Packed Days, not by the figure shown: grey up to five, amber at six or seven, red at eight or more. So a stretch reading 5.4 days on trail turns amber, because packing it means carrying six days of food. Grey means five days or fewer — a manageable window, no action needed. Amber means six to seven days — a heavy segment; consider pack weight and food compression. Red means eight or more days — an extended stretch; consider adding a resupply stop, electing a mail drop, or adjusting your pace. Carry windows update automatically as you change pace settings or modify your route.
We calculate the exact decimal days it takes to hike each section based on your active Zone Paces. Then we add a 0.25-day safety buffer and round up to the nearest whole day. This accounts for partial nero days entering and exiting towns so you never arrive at a resupply running on fumes.
The figure on each carry row — 32.3 mi · ~1.4 days on trail — is Raw Days. Your arrival dates are neither Raw nor Packed: the timeline engine starts from Raw Days, then adds the Stop day for each stop and rounds to whole days. That is why the dates always sit a little further apart than the carry rows imply.
Arriving at a town costs miles. These sliders let you model the classic Nero-in/Nero-out strategy: hiking into town, doing chores, sleeping in a bed for one night, and hiking out the next day. Only add a Zero day if you are taking a full day off trail. If you are hiking a short day in and out of town, lower your Stop day mileage here instead — that models the same thing more accurately. The app automatically absorbs the lost hiking hours and pads your total trip length, keeping your future ETAs and mail drop deadlines perfectly accurate.
A zero day means no miles hiked. When you add zeros to a town, the app inserts those days directly into the timeline and shifts every subsequent arrival date forward by the same count. Mail drop send-by dates, carry calculations, and the estimated finish date all update instantly. Zero days do not affect carry windows — segment carry calculations are based on hiking distance between resupply stops, not rest days taken.
The 'Send By' date is your shipping deadline: 14 days before your estimated arrival at that town. This follows the Pacific Crest Trail Association's own guidance, which asks hikers to mail resupply boxes no more than two weeks ahead of their expected arrival — early enough for Priority Mail to clear transit to a remote post office, late enough that the box is not sitting on a shelf for a month.
Two weeks is a ceiling, not just a deadline. Shipping much earlier than your Send By date does not make the box safer. It makes it more likely to be returned before you get there. If you are behind schedule, shipping closer to your arrival is the better error.
Hold periods. USPS holds General Delivery mail for up to 30 days. Packages are additionally subject to a shorter 15-day internal rule, which is why every ThruSmith label reads "Hold for PCT hiker – ETA [date]." That notation is what tells a clerk to keep your box rather than return it. Write it on the outside of the box as well as in the address block.
Private businesses — hostels, resorts, outfitters — set their own hold policies and often charge a fee. Confirm directly with them before mailing.
ThruSmith dates are estimates. If your pace changes significantly after shipping, call the post office or business to confirm the box is still being held.
Zone boundaries determine which difficulty index applies to each mile of your plan. Boundary miles are taken from the PCTA centerline; where a zone break is a matter of judgment rather than geography — the Sierra ending at Echo Summit rather than Sonora Pass — we follow common thru-hiker usage and say so. All mile markers are NOBO (northbound) from the southern terminus at Campo.
PCTA measures the trail at 2,655.8 miles and uses 2,650 as its published shorthand. ThruSmith stop and trailhead miles follow the measured centerline; the northern terminus is currently expressed on the 2,650 shorthand, which we are aligning to the measured value in the next data release.
All trail mile values shown in ThruSmith — stop locations, trailhead entries, carry distances, and send-by date calculations — are derived from the PCTA Centerline and Mile Marker dataset, maintained by the Pacific Crest Trail Association and hosted on their ArcGIS FeatureServer.
This is the authoritative source for PCT trail location and mileage data. The centerline was originally built from the Halfmile Project's survey-grade GPS data and has been updated annually since 2021 to incorporate reroutes, trail reconstruction, and alignment corrections. The dataset is maintained by PCTA's GIS Specialist and released each January.
ThruSmith reconciles its stop and trailhead mile values against each PCTA annual release. Mile markers in the app reflect the most recent PCTA centerline as of the reconciliation date below. Because the PCTA adjusts mileage annually as reroutes are completed, values may shift slightly from year to year — and may differ from third-party apps and guidebooks that are on different update schedules. If you notice a discrepancy between a ThruSmith mile marker and what you see on trail, please use the feedback button to flag it.
Dynamic hike planner
Don't overthink it. ThruSmith is dynamic — you can recalculate your pace, change your start date, and adjust your route at any time.
Every stop re-checked against operator sources in August 2026 — one sweep, whole trail. Next full sweep January 2027, before the season starts.
Tell us and we'll fix it inside the season — corrections don't wait for the next sweep.