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OK to make text, buttons, etc. larger on iPad than corresponding iPhone app?

Is it common to make user interface elements (text, edit boxes, buttons, etc.) larger in an iPad app than in the corresponding iPhone app? Would it violate any Apple UI guideline to do so?

I'm asking because we have an iPhone-only app now and some users really like using our iPhone app on an iPad Mini. They like the large text and large buttons when it's in "2x scaled" mode.

Our users are delivery drivers who primarily use the app for viewing the contents of delivery orders and doing numeric data entry in the field, so data entry efficiency is really important to them. We've even built a customized numeric keyboard to squeeze every possible bit of efficiency.

Now we're designing an iPad-native app. We want to do this because we want to capture edge-to-edge screen real estate that we can't with the scaled iPhone app. Also, we get a lot of support calls from users who try to install our app on an iPad and can't find it in the app store because they need to filter their search to iPhone apps to see it!

As we design the iPad app, based on our user feedback that larger is better, I want to make our UI elements larger than the iPhone version.

We're also going to do design work to leverage the additional capabilities and real estate of the iPad, but there's lots of good info available elsewhere for the general "how do I port my iPhone app to iPad?" where the generalized answer is "you redesign it!". That general question isn't what I'm asking here. Instead, I'm wondering if there's anything inherently bad about scaling up the interface elements on an iPad app, given that most iPad apps I've seen don't do this.

I don't think we need to blow everything up 2x, but instead I want to test various different scalings with users to see which size they like best. I suspect we'll end up with around 1.5x as the sweet spot between gaining efficiency via large UI elements and gaining efficiency by avoiding scrolling.

Anyway, some questions:

  • I'm worried about the nav bar having smaller text than the rest of the app. Should we scale the size of the top nav bar along with the rest of the app's UI? Or is it best to leave the nav bar text size consistent with other apps?
  • Are there any documented (or not) restrictions by Apple for larger-than-normal UI element sizes for iPad apps?
  • Beyond calculators and phone dialers, what other kinds of iPad apps use large-size UI elements like I'm describing?