Help with roof area calculator


Hello guys.

I am a programmer and I created an free website for calculating the surface area of a roof.
It is intended to be very easy to use - it just requires Length of the roof, Width, and Height (most of the time). And I am using mathematical formulas to determine the other dimensions.

Website is

Now I am not a native speaker of English so my request is if you could help me with the translations of the technical terms.
I am not sure when is correct to use "roofing area and when “roof area”.
Also i am not very sure I named corectly the roof shapes.

Another thing you can help is by requesting features - I can implement more stuff if you tell me what this industry requires.

I looked trough your FAQ and I hope this post will be approved.

Many thanks and can’t wait to hear from you



Very cool. I will be trying it out on my next estimate, I will let you know what I think then.


Very nice. Where are you located?


I am from Romania.
I lived for a short while in London but now I am back to Bucharest.
However, that might not be for long as communists and Russia are taking over, again, so I am thinking to move away for good.
Nasty thing this communism. Romanian people are the second country by number of refugees after Syria only that we dont have a war here we only have so much corruption and Russia…

I am happy you like my roofing calculator.
Are you allowed to build your own houses in US? (are you from US?)
I am asking because this roofing calculator is quite useful here as we build our houses as we please so people think how they would like their house and try to do some small calculations… Not the same can be said in other countries. In London all the houses are pretty much the same - I had such a shock when I first arrived in London. So - in such countries where big companies build 1000-2000 houses, this DIY roof calculator might not be very useful.
Only for re-roofing jobs maybe…


Welcome to the site.

Russia hasn’t been a Communist country since 1991.


I looked at your roofing area calculator briefly. You have a nice mathematical mind. There are a couple of issues I see. Determining the height difference between the eaves and the ridge isn’t that easy to measure. And many roofs have very complex geometries with multiple elevations (varying eave and ridge heights). I think your calculator could work for relatively simple roofs. However, relatively simple roofs are easy to calculate anyway.

I am not trying to be a Negative Nellie on you. You asked for feedback and I’m trying to give you honest answers. Our roofing industry is flooded with various roof calculation tools already. It would be a very tough nut to crack.


Thanks very much for feedback Dad - it is really appreciated.

This is not intended as a very precise roof area calculator - but more as an estimator for when someone might think to start working on a roof.
However, I think it is more precise than the existing online roof calculators which ask for house area and roof pitch.
Obviously when you start a roofing job and you want to buy materials, you need to use a professional roofing calculator - which I dont think there are free or online are they? The more professional tools you are talking about are paid and they are full applications and also are not very easy to use? More like the ones architects use? Obviously I cannot compete with those.

But for my objective - to make a better calculator (estimator) - free, online, easier to use and a bit more precise than the existing ones - I hope I am on the right track. I am also developing new modules as we speak - I will release a new page in a few days with pitch calculator - I see all calculators have this even if my calculator doesn’t needs a pitch… but it looks popular :slight_smile:

Other feature I am thinking to implement is to provide a perimeter and all dimensions of the roof - like rafter length etc on the fly.
And then a roofing materials calculator (estimator) based on the surface and all dimensions.
But here I might need to join someone who is in the field as my knowledge is very limited - I am barely learning the terms here :slight_smile:

So thanks again very much for your feedback - I think the height difference between the eaves and the ridge is called roof rise? Or is that only the height inside the attic? I will think if there is a better way to get this - might need a clear picture.


Alex, I respect your ingenuity and passion. The roof sketch apps and services available now are quite accurate. I’ve used them thousands of times and subsequently tested the accuracy based upon ordering materials based upon the dimensions obtained from those reports. They’re relatively cheap and fast.

I’m not trying to discourage you, just present you with reality as I see it. Finding the height between the eave and the ridge, with any reasonable precision, is a non trivial task, especially for a hip roof. Suppose there is a long rafter length, how would you propose obtaining that height difference? How would you propose doing it with roofs such as what I’m showing below?

These types of roof architecture are not at all uncommon. And far from the most challenging. These are roofs my company builds on a weekly basis. Two of those shown were built in the past two weeks (you’re seeing before photos). Again, from what I can understand, a key element in your calculations is to know the difference in height between the eave and ridge. The roof in the last photo I showed you has a minimum of 8 different eave and ridge elevations. I sketched this roof myself using a tool called RoofSnap. Below is one page from the roof report showing the sketch and measurements:

You should also take note of all the overhangs that are involved on a roof such as this. How would you propose to include those in your calculations? They can account for a significant amount of roof area on a roof such as this. This roof ended up being 68 SQ of field shingles, 4.67 SQ of cap and 1.67 SQ of starter. We ordered 70 SQ for the field shingles and the exact amounts I mentioned for cap and starter. I build in a fudge factor because it is better and more cost effective for everyone involved to have a small amount left over than have to run after more materials. Even at a 2 square difference, we’re talking accuracy of about 3%. Reality is, with the fudge factor I use, we were pretty much dead on.

I hope this helps your understanding of what challenges you may be facing.


That looks really complicated Dad.
But I have no intention to try to estimate such complex roofs - I am not considering to go that route.
This tool is intended for estimations on most common shapes - but still an improvement over the existing online tools.
I dont even think is possible to do such complex tool in browsers - that complexity requires different tools.

I tried to do a house planner in the past which was a bit more complicated and it didnt worked for this reason - the online tools are not working well for complicated calculations and designs.
This planner is quite old and I didnt updated it but it is designed to give you all the wall dimensions - external walls, internal walls - with or without the window and doors holes. But nobody was using it so I kinda abandoned it.
It is a few years old like… 7 years old and back then there was no collision detection available so I had to invent it (for colliding the rooms). Not sure any online libraries does it now.
The idea is that - complicated stuff - needs a custom application - not a website - I learned this already so I wont try to go there with the roof calculator.


Alex, thanks, I understand better now. As I stated before, if the roof is simple, it can be measured easily and in a very short period of time. Rectangles and squares are L x W x Pitch Factor to determine roof area.

Good luck to you Alex.


Thanks Authentic_Dad



We made a few updates to our calculator.

  • We are trying to give you more data other than the surface area of the roof - because we can calculate all the lengths and angles.
    Unfortunately we ran into some issues with how to explain which numbers are what. So this is a bit under review - we are looking at ways to better make this available for the users.

  • We created a few pitch calculators - pretty standard stuff but we thought you might find them useful under the same page

  • The most important feature we think - is the shingles calculator
    You can configure the dimensions of the shingle and also we added filters like shingles pack size, estimated losses, overlapping.

Again - please let me know what you think on those - I am a programmer with little knowledge on the roofing. Please let me know if you would need some more fields or if you see anything odd.

Best regards


Alex, what kind of code languages are you fluent with? Can you do web apps using Angular Java Script? Have you created any CRM’s?


Yes I can do web apps. not a big fan of Angular tho - it is for larger applications and lately since I opened my own company I only do smaller stuff.
I do all sort of web related languages but mainly PHP, Laravel, Cake… js, Jquery, Vue which is lighter than Angular, databases, Linux and all the other. 15 years as a programmer still running as new :slight_smile:
I have created also a CRM like a few months ago (all by myself - not mentioning I mostly worked for such project as employee) - it is a news application which has some innovative features like it lets the users break the content of the articles into chunks which the users define and then the other users vote each chunk which then you can see in a visual representation like a tree. (Not sure if I should put a link I dont want to abuse the friendliness of this nice forum)
Cant find a client for it yet - I am bad as a salesman - I was doing way better when I was an employee - financial speaking :slight_smile:

If you (or anybody else) need any advice on web related stuff I will be more than happy to help - just let me know.


Hi guys,

I implemented the feature where you can get all the dimensions - lengths, surfaces angles and shingles for a roof.
When you get the surface area of a roof, below you have all this data.
I hope is easy to read - I could not find a better way to do it.

And with this I kinda ran out of ideas what to do for this roofing calculator.
Waiting for any suggestions as always.

Best thoughts