USPS: USPS's own numbers
USPS publishes its service standards, the number of days it aims to take, for every pair of 3-digit ZIP areas, with exceptions for specific 5-digit ZIP codes. We use that data directly for First-Class Mail, Ground Advantage and Priority Mail, marked "USPS standard". When some addresses in an area take longer, we show a range. Current data: effective November 1, 2026. Priority Mail Express isn't in USPS's files, so it's an estimate.
UPS and FedEx: estimated from distance
UPS and FedEx don't publish their transit tables as data. Each ZIP code's first three digits point to a processing area; we measure the straight-line distance between your two areas and place it in zones 1 to 8, local to cross-country. Then we match it to each service's published window: UPS and FedEx Ground take 1–5 business days, longer for longer distances. Air services like 2nd Day Air take a set number of business days wherever they're going.
Postage
Postage prices come from USPS Notice 123, effective October 4, 2026, and zones from USPS's National Zone Charts Matrix. We apply USPS's rules for rounding, dimensional weight and size fees. They're retail prices; online label services are often cheaper.
Calendar rules
Arrival dates follow each carrier's calendar: USPS counts Saturdays and skips Sundays and federal holidays; UPS and FedEx count weekdays and skip their holidays. More on how days are counted.
Holiday deadlines
The last-day-to-ship dates come straight from USPS's and FedEx's published 2026 schedules and UPS's air-service dates. UPS publishes no single Ground date, so for UPS Ground we count back business days from your route's typical transit time, and say so.
Where estimates can be off
- Network quirks. Carriers route through hubs, so two nearby ZIP codes can sit in different networks, and A to B can differ from B to A.
- Alaska, Hawaii and territories. Ground shipments travel by air or barge and take longer than the mainland numbers. We flag these routes.
- Peak season and weather. Mid-November through December, and storms, add delays no estimate can predict.
- Rule changes. USPS revised its service standards in 2025, and carriers change services and prices regularly. We recheck and date our information.
When to use the carrier's tool
For anything that can't be late, like legal documents, medication or a deadline, confirm the date with the carrier's own tool before you ship, and choose a service with a guarantee.