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Convert design evolution

by John Casasanta
August 24, 200958 comments

What happens when you stick a few people who can’t agree on anything at first… but later agree on everything… in a virtual room to do some app design? This is the result:

I had originally planned to do a post detailing the design of Convert… from my assy “programmer mockup”… until the finished app. But I figured that this would be much more fun and 1000x less long-winded. :P

We’re ecstatic that Convert broke into the App Store top 20 this weekend after a fairly quick rush up the charts! Check it out if you haven’t done so yet. People really seem to be into the UI. My favorite reviews are the ones that include tidbits like the following excerpt… these put a huge grin on my face:

“Apple couldn’t have done it better had they tried.”

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We’ve been creating top-notch apps since the App Store first opened. Our apps are used by literally tens of millions of people in all corners of the world. A few of our favorite and most popular apps we’ve created are:

Who linked to this


  1. HolyJuan
    9:26am, August 24, 2009

    That was wonderful to watch. And it’s amazing that all that design all happened in under a minute at 9:42am.

  2. Florian
    9:38am, August 24, 2009

    I always love evolution videos like this. Thanks for sharing a insight to your work!

    Greetings from Germany

  3. idogcow
    9:40am, August 24, 2009

    Wow - I kept thinking that was the look they should have used, no wait… that one up to the end. Congrats on a well done app and for the peek behind the veil.

  4. Rintaro
    4:45pm, August 24, 2009

    Great to see how much effort you guys made on the app. No wonder the app is so cool looking!

  5. heppi
    2:37am, August 25, 2009

    Wonderful app design. But 1 square kilometre is not 1000 square metre. it is 1.000.000 square metre :) see 1:30 in the video

  6. Stephane
    8:34am, August 25, 2009

    Wonderful! Really nice app btw!

  7. Dr. Noel Enete
    9:25am, August 25, 2009

    Wonderful tour through your UI process. If you don’t mind my asking, what tool did you use to generate the video? Especially how do you show those burst circles to indicate screen touches?

  8. Jeff
    9:37am, August 25, 2009

    I would love to see how the app’s icon design has evolved as well :) I am not totally digging the icon right now, I feel like there’s ways to make it sleeker looking, much like the other tap tap tap products’ icons. But then again I’m not a designer, so heh.

  9. sengan
    11:17am, August 25, 2009

    Very nice video.

  10. Eyhk
    12:07pm, August 25, 2009

    Very interesting! It shows the train of thought very nicely and it even made me start rooting for certain design elements (like the color contrast between left and right conversions and the arrow inbetween) and gave me satisfaction when they made it to the final product!

  11. David Taylor
    12:12pm, August 25, 2009

    Great video. Immediately bought the app!

  12. Clay
    12:20pm, August 25, 2009

    Did Convert start in wireframe, or was it not really necessary for this project? I suppose it’s probably less important when you’re designing a UI that’s almost more object than software, but I found the evolution of functionality in parallel with visual presentation interesting.

    I mean, that’s something I do all the time but I’m technically not supposed to. :)

  13. Matt
    1:22pm, August 25, 2009

    2 requests: (Re)implement the delete button, and Sexier icon.

    …one of those is more important than the other.

  14. chevap
    1:22pm, August 25, 2009

    beautiful. bought it instantly. omg, i feel like a woman now.

  15. Joshua Mormann
    1:22pm, August 25, 2009

    Thanks for posting this, what an awesome design evolution.

    I love the app myself—I use it! It’s not an all the time app, but the brilliantly intuitive UI makes it so quick, and easily usable even if you only use it once in a while. It’s perfect.

    Great work, and thanks again for sharing the evolution like you did. It was great to watch.

  16. punkassjim
    1:28pm, August 25, 2009

    Absolutely wonderful. This video is the reason I’m really, REALLY wanting this app right now. I’ve already got a visually stunning conversion app with very good UX (ConverBot Mini) which I have never actually needed to use. So, if my willpower loses out, you’ll get my 99¢ simply because of my appreciation for this video and your design process.

  17. rootman
    1:40pm, August 25, 2009

    Great app, have been using for a couple weeks and the thought and effort really shows through. Everything I wanted but didn’t get from the other conversion apps I tried.

  18. Michael Ward
    2:17pm, August 25, 2009

    Bought it because I love to see the effort you put in - and the final results are wonderful. Too many developers/UI designers chuck something down and decide that its good enough, without doing enough iteration.

  19. András Puiz
    2:30pm, August 25, 2009

    Amazing indeed.
    Too bad that someone’s bad idea at 0:37 prevailed, and the widget displaying the value remained in a pretty, but usability-wise horrible location.

  20. Scott Barnes
    3:01pm, August 25, 2009

    Inspiring … well done

    Scott Barnes

  21. Wes Mitchell
    3:08pm, August 25, 2009

    Excellent Video. I bought the app the day that it came out (I am on the email list) keep up the great work!

    Wes Mitchell

  22. cefstat
    3:38pm, August 25, 2009

    Two remarks after playing with your program for 5 minutes.

    Kilograms (kg’s) do not measure force but mass. You can relate kg’s to Newtons since the force exerted to 1 kg (at some point) on the surface of the Earth is about 9.8 Newtons. In your application you convert 1 Newton to 980665 kg which is wrong in so many ways.

    The second remark is that 980665 appears in your application as 980,665. This is fine for Americans but very confusing for (most?) Europeans. For us 980,665 is 980 + 665/1000.

  23. David
    3:39pm, August 25, 2009

    I already have a free unit converter that does everything I need it to do, but I just bought this anyhow because of the video. Great work!

  24. Tom
    4:15pm, August 25, 2009

    Cute little app, but I’m almost as impressed by the refreshing break from the typical video aspect ratio.

  25. firmum
    5:03pm, August 25, 2009

    A very pleasing app to use, I have to congratulate you on producing such a nice presentation for a unit converter. Unfortunately, it suffers from a few shortcomings to make it a great application:

    - There is no way to correct a typo, where is my delete button to undo the last digit entered?

    - Adding two different units is a bit too complicated: enter number for first unit on the left, scroll to second unit on the right, tap on the right side, press + and the number for the second unit, and so on. This will lead to repeated errors, as my thinking goes one day “plus” “one” “week”, but I have to enter “select week”, “plus”, “one” (and if do “plus”, “select week”, “one”, my previous sum is wiped out)

    - I believe you are missing out on a relatively easy way to score points with non US users: Put the local currencies for the selected region of the device to the top of the list. After all, 90%+ of the time you want to convert from/to your native currency.

  26. Qingdi
    6:56pm, August 25, 2009

    Good work, very nice. UI is so magic.

  27. Sky
    7:12pm, August 25, 2009

    Didnt by shit but love the idea of the video

    Get updates on whats New with Graphic design, typography, the arts, architecture, industrial design, music……………… Contribute by simply sending me articles to post or creating a discussion. Tell your friends to become a Fan. Spread the news like people spread syphilis!

  28. nuvs
    7:22pm, August 25, 2009

    Saw the video, bought the app!

  29. Jim
    9:09pm, August 25, 2009

    I appreciate the video, and I bought the app, but I was overall disappointed with the lack of interaction polish (as opposed to visual polish). Some examples:

    · your finger obscures a lot of screen while scrolling around… you routinely have to either get the finger up, or scroll awkwardly in bits and pieces

    · the lens effect on selectors seems confusing at times, especially combined with the above

    · if you hold and swipe to change the category, the categories should hide as soon as you release your finger. Now you have to wait a while for the numbers . What’s worse, type-ahead doesn’t seem to be working either in many cases

    · categories expanding full screen is actually jerky, even on 3GS

    · no backspace button, just clear. What if you make a mistake during the last digit?

    · the tap target on the refresh button for currencies is too small – I oftentimes end up activating the category instead of refreshing

  30. Brad Bratton
    11:04pm, August 25, 2009

    What doe the energy app do? Does it give KWh’s for electricity and calculate mils for commisison structures? Anyone? I sell electricity and would love to calculate different profit opportunities.

  31. mikelangelo
    11:12pm, August 25, 2009

    Thanks for that post. It was great to see the iterative process and how over the course of many large and progressively more subtle design decisions, an excellent UI was developed. Very cool.

  32. rgw
    2:18am, August 26, 2009


    Seriously, I’ll be buying this app as soon as my phone wakes up from losing power (in the wall charger now). This also is a great example of iterative design in motion. Great work ya’ll!

  33. FAN of taptaptap
    3:03am, August 26, 2009


  34. jason
    7:17am, August 26, 2009

    Glossier than Joan Collins on a formica table eating a caramelised cherry.

  35. Sven
    7:51am, August 26, 2009

    First unit converter that I actually like, thanks!

    But it seems a bit slow for app with sole job of performing simple arithmetic calculations. Iphone’s Calculator App starts with a split second, Convert not…

    Also - please add more currencies. Please!

  36. Alex Dahlem
    7:52am, August 26, 2009

    Although i am not an iPhone User, i really loved seeing that process. Great example, thank you!

  37. Robert Rawlins
    7:52am, August 26, 2009

    Ah this is excellent, one of those ideas I wish I had first ;-) well done guys, cool beans.

  38. simonjs
    7:57am, August 26, 2009

    Wow, so many different permutations, thanks for sharing. Your apps all look great, well thought out and well finished - I can see why!

  39. Ian Storm Taylor
    7:58am, August 26, 2009

    Awesome video to watch. Luckily those two didn’t agree on anything eh? Makes me want to go out and try to design an app now…

    Keep up the good work. Beautiful end result.

  40. Honest
    8:14am, August 26, 2009

    A design masterclass! - well, maybe not, but a really interesting video full of insights nonetheless.

  41. Brigg
    8:28am, August 26, 2009

    I think this is a great example of how difficult and time consuming it is to design a great UI.

    Also, not sure if this is the right place, but I’d really love to see some additional units such as the following:

    Volumetric Flow

    I really like the UI, but I think that Concrete Software’s Unit Converter offers more conversion types.

  42. Grover
    8:50am, August 26, 2009

    The irony of not being able to watch this on an iPhone is not lost on me.

  43. Most Interesting Ideas
    9:05am, August 26, 2009

    Good work

  44. Franky
    11:35am, August 26, 2009

    Agree with Grover. Ridiculous that a blog from a great iPhone app developer doesn’t embed the video in a format viewable on the iPhone.

  45. Panotzki
    12:49pm, August 26, 2009

    Good job Kev! Love the interface, nice eye candy.

    Being an “international” guy, I can see myself using it a lot for the currency conversion. All other things I will just use occasionally.

    One tip is to somehow limit the list of currencies. Although an impressive list, it is just too tedious to scroll through Swahili Balubas etc when I know I’m mostly interested in 3-4 currencies, USD, SEK, PLZ and Euro…


  46. parabel
    1:01pm, August 26, 2009

    What’s the name of that “song” / piece of music? :)

  47. Sven
    2:15pm, August 26, 2009

    One more thing - it would be nice to have fuel economy units in Convert. You know, the miles per gallon / litres per 100 kilometres and British miles, US miles thingie.

    Anyway - please steal the list of supported units from Convertbot ;)

    It is really excellent in that matter. Its rotating UI is pure gimmick, though.

  48. Jacco
    4:40am, August 27, 2009

    Just wonderful, this is like peaking into the chefs kitchen to see how he actually makes this wonderful gourmet. Great stuff, great insight!

  49. Markus
    9:54am, August 27, 2009

    Pleasure to see all the versions during the design process. Great!

  50. Tyroga
    11:24pm, August 27, 2009

    I already bought another conversion app, but laid down the $2.49 Australian on this app purely cause I loved the way it looks. And if I’m honest I so rarely need any conversion tool… not to mention the fact that besides the other one I bought, I already had another that was free. :P

    Convert is my fave.

  51. Alaska Web Design
    11:17am, September 2, 2009

    I’m really surprised at how much money developers can make with these small apps. We have a friend who recently retired after creating a simple app.

    It’s nice to see people say: “I really don’t need to worry about money any more.”

  52. Favoriten
    9:34am, January 4, 2010

    Nice Work

    Big Thx for this

    Greeetttzzz Membre

  53. Peter O'Brien
    3:49am, January 7, 2010

    I have purchased your excellent app.

    However PLEASE add “fuel consumption” - MPG to l/100km and reverse - very useful in some countries if not US and others have asked for it. No-one else does it but it will be a selling point for many.

    THank you

  54. D8ednarz
    6:10am, January 16, 2010

    Despite many request for PLN to be added within currency converter it seems that they fall on deaf ears??? John, is it really that difficult to add a feature so often requested by users of your software. Do not treat it as a blackmail however I don’t think I’ll buy from the company which doesn’t listen to customer feedback, no matter how beautiful your products are.

  55. Xander Myers
    8:49am, January 21, 2010

    Love this app and it amazes me often you find a use for it day-today. That being said, for me there is one thing missing.

    In the typography section, could you please include an option to convert ‘em’ (or point it out to me if I have overlooked it). Working between ‘px’ in print and ‘em’ on the web can be a pain to translate. It would be great to be able to use Convert to take the hassle out of it.

    Congrats and Thanks!

  56. UI Design
    6:28am, March 10, 2010

    that’s really a fantastic post ! added to my favourite blogs list.. I have been reading your blog last couple of weeks and enjoy every bit. Thanks.

  57. Vu
    10:16pm, October 16, 2012

    When is the update for iPhone 5 going to come out as the screen proportion is not correctly displayed when in portrait mode.

  58. George
    6:54am, October 19, 2012

    Needs an update!

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