I have been using the same graphics shop for 15 years-He has the Union Jack programme in his computer- He cuts the red and blue sections then applies it to the white roof- $60.00 and l'm on my way-

His only stipulation is, bring me a mini with a white roof-

BIG AL

Union Jack roof decals are made in sections for a reason - the complex curves of the roof make it very very difficult for even a professional to get a one-piece roof-sized bit of vinyl applied properly.
If you are attempting a complicated design, be prepared to either cut bits out as it crinkles up or stretch it around the curves.

I would hesistate to have a graphic made based on straight dimensions.   As jedduh01 mentioned, the MINI roof has complex curves.  If your MINI has a sunroof - it adds another dimension.

Good luck!

Thank you for the info.

I'm working with a Graphic Industry to do this so they ask me for specific measures.

buy a cloth tape measure from a hobby store. They're made of soft plastic now not cloth, but flexible like cloth unlike a carpenters tape measure. And................bob's ya uncle.

The word I was looking for and could not remember.  Crafts store. that's where you'll find a 'cloth' tape.

Front gutters are two inches WIDER in the front than the rear gutters on a mini. (ive made roofracks, They are not squares)

Now decals and vinlyls even get more complicated with the fact of the curve and takeup. of that distance. 

We dont know who you are working with to get this done - but typical vinyl projects consist of making it Oversize then trim to tuck and fit.

Streching vinyl over compound curves with 1 piece of vinyl is not for the faint of heart. Hope you have the experience to apply. True vehicle Wrapping vinyl is the best matearial to use with the strech and the color allowances. 

Basiclally - 46 x whatever long - will cover your roof- add a few more inches for over lay and tuck in both directions. 

Center decal - apply - trim all edges. 

Yes in fact I have 2!!! but if you see your mini you'll see that is not completely  uniform and because the one I own doesn't have a roof decal I not able to send the dimensions to company that is going  to do the anniversary decal.

And If I’m asking for help is because I need it not just for fun!!!

Ummm... do you not have a tape measure ?
You have the Mini already.

Hello, I own one classic mini 1999.

For our aniversary I want to make a special roof decal for my wife but I don't know the real dimension of my roof if I want to put a decal like the one's with the union flag decal.

Can anyone help me with some information ?