How long does it take to build an app?

Most first versions of an app take three to four months from the day the scope is agreed to the day it is in the stores. Simple ones take less. Anything with payments, live location or two sides, like riders and drivers, takes more.

That's if nothing waits on anybody. It usually does.

Where does the time go?

Roughly like this for a typical app.

1. 01Weeks 1 to 2. Working out exactly what it does, and designing every screen. You sign the screens off.
2. 02Weeks 3 to 8. Building. You should have a test version on your own phone in this stretch, not at the end.
3. 03Weeks 9 to 11. Payments, the awkward edge cases, and real people testing it.
4. 04Weeks 11 to 12. Store submission, review, fixes, launch.

Notice the building is about half. The other half is deciding, testing and getting approved.

What makes an app late?

In my experience, the same four things.

Changing the scope halfway. Every new idea in week six pushes the end back, and the new idea is never small.

Slow answers. If the developer asks a question on Monday and gets the answer on Friday, you've lost a week for one question.

Accounts. Apple and Google want a registered company, and sometimes extra paperwork, before they let you publish under the company's name. That can take weeks and has nothing to do with code. Start it on day one.

Review. Apple checks every app before it goes live. If the reviewer can't log in or doesn't understand a permission, it comes back.

How long does app store review take?

Usually a day or two per submission. The risk is not the wait. It's the rejection that sends you round again.

Our first submission of SayScope came back. The reason was a background audio setting we had inherited from a library and didn't even use. A small fix, and it was approved. Now we check for that before we submit anything.

You avoid most rejections with boring preparation. Notes for the reviewer. A demo account that works. Clear wording on every permission the app asks for.

Does building for iPhone and Android double the time?

No, not if it's built properly. We build both from one codebase, so the second platform adds days of testing, not months of building.

What it does add is a second store, with its own account, its own rules and its own review. Plan for both from the start, even if you launch on one first.

Can it be done faster?

Yes, by building less. That's the only honest way.

A first version that does one thing well can be out in six to eight weeks. An app that tries to do everything on day one takes six months and launches tired.

Anyone promising a full custom app in two or three weeks is selling you a template. Sometimes that's fine. Just know what you're buying.

What can you do to keep it on time?

• Agree the screens before the build, and don't reopen them.
• Name one person who makes decisions, and answer within a day.
• Open the company, Apple and Google accounts in week one.
• Ask for a test build on your phone every couple of weeks.
• Have ten real users ready to test before launch.

Do those five and the timeline you were quoted is the timeline you get.

That's how we run it on the apps we build. If you want a real timeline for yours, tell me what it has to do.