Hour estimates for app development vary by an order of magnitude for the same brief, and the variation is mostly about what each bidder assumed rather than how fast anyone works. That makes the headline number nearly useless for comparison and makes the assumptions underneath it the thing actually worth reading.
How long does an app take to develop, and what makes the same app take four times longer
One platform or two. Whether the backend exists or has to be built. How many user roles see different data. Whether third party systems are integrated and how well documented they are. Whether designs exist and are complete. Whether offline operation is required. Whether the product handles regulated data. Each of these can double a figure, and a quote that does not state its position on all seven is not an estimate, it is a hope with a number attached.
How long does it take to build a mobile app? Judge the estimate, not the total
Ask each bidder to break the estimate down by feature area with its assumptions written beside it, and to name the three things most likely to make it wrong. A bidder that identifies its own risks is far more likely to deliver near its number than one presenting a confident total. Then compare the assumptions across bids: you will usually find the cheapest bid assumed away the most work, which is a scoping difference rather than a price advantage.
What agile mobile application development should mean in your contract
Not a methodology name, but three observable behaviours: working software demonstrated every couple of weeks, direction changes absorbed without a change order within an agreed budget, and early honest reporting when something is behind. Write those into the agreement and ask for the actual cadence of the bidder's last three projects. Agile used as a reason not to estimate at all is a different thing wearing the same word.
How to choose a mobile app development company, in the end
Shortlist on relevant delivered work, then buy a small piece of real work from two finalists before committing. Two or three weeks of genuine delivery tells you how they ask questions, how they handle ambiguity, whether their estimates mean anything and what their code looks like. That is worth more than every proposal document and reference call combined, and it costs a fraction of the mistake it prevents.
Questions people ask about how many hours does it take to develop an app
So how many hours to develop an app should we expect?
The range is so wide that the number is not useful without assumptions. One platform or two, whether the backend exists, how many roles see different data, integrations, whether designs are complete, offline requirements and regulated data each can double the figure.
How long to build an app, and how do we compare estimates fairly?
Compare assumptions rather than totals. Ask for a breakdown by feature area with assumptions written beside it and the three things most likely to make it wrong. The cheapest bid has usually assumed away the most work.
What should agile mean in the contract?
Working software every couple of weeks, direction changes absorbed without a change order within an agreed budget, and early honest reporting of slippage. Ask for the real cadence of the last three projects rather than the methodology name.