Methodology
How We Calculate Roaming Savings
Every savings figure on this site is the result of a documented process. We pull carrier roaming rates from official sources, collect eSIM plan prices from provider websites, and subtract one from the other. No estimates. No assumptions.
Where carrier rates come from
We track roaming rates for 6carriers, including AT&T, Verizon, T-Mobile, EE, Vodafone, and Xfinity Mobile. Each rate is pulled directly from the carrier's own international roaming page. We record the daily pass price, per-MB overage cost, and any speed throttle that applies. When a carrier uses zone-based pricing, we map each of our 207 destinations to the correct zone and store the zone rate for that country.
We do not accept carrier-supplied data sheets or press releases. Every rate is read directly from the public pricing page and timestamped. If the carrier updates its page, our next monthly pass picks up the change and we update every affected destination within 48 hours. See the full carrier rate breakdown.
How we collect eSIM prices
We check prices across 5 eSIM providers weekly. For each provider and destination, we record every available plan size and duration. We use the cheapest plan that covers a typical seven-day trip with moderate usage (roughly 1 GB per day) as the baseline comparison point. Larger or unlimited bundles are shown when they represent better per-day value.
The four providers we track are Airalo, Holafly, Saily, and Nomad. Each was selected based on global destination coverage and the number of supported countries. We do not accept payment from any provider to alter which plan appears as the cheapest option. Compare eSIM providers.
The savings calculation
The savings number on each country page follows a fixed formula. We take the carrier's total cost for a seven-day trip (daily pass multiplied by seven, or per-MB rate multiplied by expected usage) and subtract the eSIM plan price. That difference is the dollar figure you see. We run this calculation for every carrier and every provider combination so you can compare across all options.
We also calculate a percentage savings figure. If AT&T charges $70 for a week in Japan and an eSIM costs $12 for the same period, the percentage is 83%. Both figures update automatically when either the carrier rate or the eSIM price changes.
Worked example: Japan, 10-day trip
Japan is one of the most popular destinations on this site and shows the formula well. Here is exactly how the savings figure on the Japan page is calculated.
| Option | Rate | 10-Day Cost |
|---|---|---|
| AT&T International Day Pass | $10/day | $100.00 |
| Verizon TravelPass | $10/day | $100.00 |
| T-Mobile high-speed add-on | $15/day | $150.00 |
| Airalo eSIM (10 GB) | One-time | $8.99 |
The formula applied step by step:
- Carrier baseline: AT&T daily rate ($10) × 10 days = $100.00
- Cheapest eSIM: Airalo 10 GB plan = $8.99
- Dollar savings: $100.00 − $8.99 = $91.01
- Percentage savings: $91.01 ÷ $100.00 = 91%
The $91.01 figure is what appears on the Japan destination page. We repeat this calculation for all three major US carriers so you can see the savings regardless of your home carrier. Run the calculator for your destination.
Worked example: UK, weekend trip
Short trips amplify the percentage savings because eSIM plans cover multi-day use at a single flat price. Here is how a 3-day UK trip works out:
- Carrier baseline: AT&T daily rate ($10) × 3 days = $30.00
- Cheapest eSIM: 3 GB UK plan = $4.50
- Dollar savings: $30.00 − $4.50 = $25.50
- Percentage savings: $25.50 ÷ $30.00 = 85%
Even on a 3-day trip, the savings exceed $25. The same logic applies to every destination in our database. The carrier pays $10 per day regardless of trip length; the eSIM plan price stays fixed regardless of how many days are left on it.
Testing devices and speed protocol
We test eSIM activation and network performance on five devices: iPhone 16 Pro (iOS 18), iPhone 15 Pro Max (iOS 18), Samsung Galaxy S25 Ultra (Android 15), Samsung Galaxy S24 Ultra (Android 15), and Google Pixel 9 Pro (Android 15). Testing on both iOS and Android matters because eSIM installation flows, QR code scanning, and network switching differ between platforms.
Speed measurements use Speedtest by Ookla. For each provider and destination, we run a minimum of ten tests across three times of day: morning, afternoon, and evening local time. We discard the top and bottom ten percent of results to remove outlier readings. The remaining values are averaged for the published figure. All speed tests use the nearest Ookla server with less than 50ms latency. Speed data is cited as “Source: Ookla Speedtest Intelligence” on destination pages.
Activation time is measured from QR code scan to the first successful data request. We screenshot each step of the activation flow on both platforms. We also run airplane mode toggle tests to measure how quickly the eSIM reconnects after toggling cellular off and back on.
Verification and update schedule
Carrier rates are verified once per month against the carrier's own website. eSIM prices are checked weekly against each provider's official app and website. When a carrier announces a mid-cycle rate change or a provider adjusts plan pricing, we update the affected pages within 48 hours and note the new verification date.
| Data type | Frequency | Source |
|---|---|---|
| Carrier roaming rates | Monthly | Carrier official pricing pages |
| eSIM plan prices | Weekly | Provider websites and apps |
| Network speed data | Quarterly | Ookla Speedtest Intelligence |
| Coverage maps | Quarterly | GSMA Intelligence, provider docs |
| Zone mapping tables | As updated by carrier | Carrier-published zone tables |
If you find a rate that looks wrong, our contact page has a correction line.
Data sources
- Carrier roaming rates: official websites of AT&T, Verizon, T-Mobile, Vodafone, EE, Xfinity Mobile (monthly verification)
- eSIM plan prices: public plan pages of Airalo, Holafly, Saily, Nomad, HelloRoam (weekly verification)
- Zone mapping: carrier-published international zone tables
- Network coverage: GSMA Intelligence country records
- Speed benchmarks: Ookla Speedtest Intelligence (quarterly verification, tested on iPhone 16 Pro, Galaxy S25 Ultra, and Pixel 9 Pro)
What we do not do
We do not accept payment from carriers or eSIM providers to adjust savings figures. We do not use estimated or self-reported speeds in cost calculations. We do not round savings numbers in favor of either option. The math is the same whether the result favors the carrier or the eSIM provider.
Primary sources
Frequently asked questions
How often do you update carrier roaming rates?
We verify carrier roaming rates once per month from each carrier's official website. eSIM plan prices are checked weekly across all four providers. When a carrier announces a mid-cycle rate change, we update affected pages within 7 days of the published change.
Do you count taxes and fees in the savings calculation?
No. All savings calculations use published base rates only. Carrier taxes, activation fees, and government surcharges are not included because they vary by account and location. The actual savings you see at checkout may be slightly higher or lower depending on your specific plan and tax situation.
Why do you use AT&T as the primary comparison baseline?
AT&T has the largest US subscriber base and uses a predictable flat $10/day International Day Pass rate across most destinations. That consistency makes it the clearest baseline for comparisons. We also show Verizon TravelPass and T-Mobile high-speed add-on figures alongside AT&T on every destination page.
What happens when a carrier changes its roaming pricing?
We update the affected destination pages within 7 days of any published rate change. Our monthly verification pass catches most changes. Carrier pricing pages are bookmarked and checked directly. If you spot a rate that looks wrong, our contact page has a correction line.
Do your savings figures account for unlimited data plans?
Yes. Where a provider offers an unlimited eSIM daily rate, we compare that against the carrier's daily pass rate directly. For fixed-data plans, we use the cheapest plan that covers a typical 7-day trip at roughly 1 GB per day as the baseline comparison point.
For more context on where these numbers lead:
Our team
eSIM vs Roaming is maintained by a team of four research analysts specializing in mobile connectivity, consumer telecom pricing, and travel technology. The team has tested eSIM providers across 40+ countries and holds over 15 years of combined experience in carrier rate analysis and network performance testing. We purchase all eSIM plans at full retail price. No provider gives us complimentary plans, press access, or preview pricing.
For more about who we are and our editorial standards, visit our about page.
Is eSIM cheaper than international roaming?
Yes, a travel eSIM is 70-90% cheaper than carrier roaming for international trips. AT&T and Verizon charge $10/day for international data, totaling $70-140 for a 7-14 day trip. A travel eSIM on the same local network costs $5-25 for the same period. Both connect to the same cell towers in the destination country. The eSIM removes the carrier markup. Rates verified June 2026.
Do eSIMs use the same network as carrier roaming?
Yes, travel eSIMs connect to the same local carrier towers that AT&T, Verizon, and T-Mobile use for roaming. When AT&T says you are roaming on NTT Docomo in Japan or Vodafone in the UK, a travel eSIM connects to the exact same towers. The difference is price: AT&T charges $10/day for that connection. An eSIM charges $5-15 for a full week on the same infrastructure.
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