It’s easy to estimate how many minutes you might use for phoning home when you’re traveling abroad. Figuring out your data needs is trickier.

“That’d be like saying before you go to Italy how many pounds of pasta you’re going to eat or how many liters of wine you’re going to drink,” said Scott Tharler, a gadget expert and blogger for Discovery News and Fodor’s. “You don’t know how many megabytes of data you’re going to chew up.”

Start by thinking about what you’ll want to do on the Internet during your trip. Simple text emails won’t gobble up much of your allotment, but streaming videos and turn-by-turn navigation will. Play around with some online data-estimating calculators, such as those from Verizon or AT&T. If you’re a gadget hound or traveling with your family, you might need to take into account how many devices will need a connection. And the number of countries you’ll be visiting will also affect your decision.

“Really, when it comes down to it, there are lots of offline resources” for figuring out travel information on the go, Tharler said, but “it’s a safety blanket knowing you’re connected to the Internet.”

Once you’ve decided just how big your blanket should be, here are some options for getting online with your gadgets:

Wi-Fi

Pros: Connecting to a wireless network is often free or very cheap. Look for hot spots listed on Wi-Fi-FreeSpot. Boingo, a wireless Internet provider with more than 500,000 hot spots around the world, offers a variety of Wi-Fi plans, including daily or monthly access and prepaid credits. Examples: $7.95 per month for unlimited access on up to two mobile devices or $59 per month for 2,000 minutes worldwide on up to four laptops or mobile devices.

Cons: Of course, you’ll need to find a hot spot and, as at home, you’ll be at the mercy of the vagaries of wireless signals. Security can also be a concern. Wired magazine suggests using an encrypted virtual private network (VPN) or at least ensuring that Web services you access have a URL starting with “https” rather than “http.”

Be your own hot spot

Pros: Forget trying to locate someone else’s Internet signal. A 4- by 2.5-inch Mi-Fi hot spot lets you set up your own wireless broadband connection — which is what Tharler said he’d do when traveling.

Some travelers may already have a mobile hot spot device from their cellphone providers, but if not, something like Xcom Global’s rental program is an ideal alternative. For $14.95 per day (plus a standard round-trip shipping fee of $30), you’ll get unlimited data coverage in any of 195 countries. The National Geographic-affiliated Cellular Abroad, Tharler’s pick for travelers who want stress-free service, offers a similar program. Rental for a trip of up to seven days costs $69, plus $59 for a credit good for 30 to 60 MB of data, and round-trip shipping that starts at $12.88. Cellular Abroad is available for more than 130 countries.

The Mi-Fi device lets you piggyback up to five Wi-Fi devices onto its 3G connection, which you can secure against digital eavesdroppers.

Cons: You’ll have another gadget to pack and charge.

Use your phone