The standard boardroom carpet width on the roll is four metres. Some ranges also come in five metres width, but the range is far more limited.
As the above suggests, you are going to have to buy two lengths and have join somewhere. Carpet fitters do this joining.
Whether your room is marginally less than five metres, allowing you to consider a boardroom of five metres, you will have to check. A significant cost of any laid carpet is the cost of the fitter, who includes the edging strips and thresholds in his quote. If you employ a fitter separately, he can make no margin on the carpet purchase so will most likely quote you a higher fit only price.
Frankly I doubt that you will end up saving money.
If you are using four metre widths, you are going to need two off lengths at 6.3m, and don't be tempted to automatically assumed you can buy a second strip of 3.15m only and cut that in half to make the required strip length. Your fitter should be approached to see if he recommends this as cost saving measure.