How to Use the Local SIM vs Roaming Calculator
Enter your trip length, daily roaming cost, and local SIM price to compare total costs. Include call rates if your roaming plan charges per minute. The calculator shows which option saves you money and by how much.
When to Choose a Local SIM
For trips of 3+ days with heavy data use, local SIMs almost always win on price. A 7-day data SIM in Europe (15GB) costs $15–$25 at airport kiosks or telecom stores. In Southeast Asia, 30-day unlimited SIMs cost $5–$15. Compare this to AT&T or Verizon's $10/day TravelPass — 7 days = $70 for the same connectivity. The catch: local SIMs mean your US number won't receive calls or texts unless you port to Google Voice or use a VoIP app like WhatsApp for calls.
When to Stick with Roaming
For 1–2 day trips, roaming is often simpler and comparably priced. If you need your US number for two-factor authentication texts from banks or work calls, roaming preserves this. T-Mobile's Magenta plan includes free international data (at 256kbps) and $0.25/min calls in 215+ countries — check if your current plan already includes international access before paying extra. Google Fi includes data in 200+ countries at domestic rates.
eSIM: Best of Both Worlds
With a dual-SIM phone and an eSIM plan, you can keep your US number active for calls and texts while using cheaper local data. Airalo offers destination eSIMs starting at $4.50 (1GB, 7 days) up to $15–$30 for 10–20GB regional plans covering multiple countries. Nomad and Holafly are alternatives. Install the eSIM before you leave, activate it on arrival, and your US line keeps working via Wi-Fi calling for free.
Frequently Asked Questions
Airport arrival halls almost always have SIM card kiosks or carrier booths — prices are slightly higher than in-city but the convenience is worth it for immediate connectivity. In-city: carrier stores, convenience stores (7-Eleven in many countries), and supermarkets. Major carriers to look for: Orange (Europe), SFR (France), Vodafone (UK/Europe), True/DTAC (Thailand), Viettel/Vietnamobile (Vietnam), Telkomsel (Indonesia).
Yes — WhatsApp, iMessage (over internet), FaceTime, Messenger, and all data apps work normally on a local SIM. The only thing that doesn't work is SMS/calls to your original home number. Set up Wi-Fi calling with your US carrier before travel (available on most plans) so when you're on hotel Wi-Fi, you can still receive calls to your US number even without roaming.
Yes — your phone must be carrier-unlocked to accept a foreign SIM. US phones bought on installment plans are often locked for 12–24 months. To unlock, contact your carrier after the device is paid off or the lock period expires. iPhones bought directly from Apple are typically unlocked. Check Settings > General > About > Carrier Lock on iPhone; for Android, call your carrier or check Settings > Connections > SIM Manager.