How Much Backing do I Need? 

This is a very common question at a quilt shop!  If you aren't sure here is another way to look at it.  

If you buy 1.5 metres of fabric you have enough to back a quilt that is 38" x 55" - and it gives you enough for 2.5" overhang all around.  That probably won't be enough for your longarmer but would be enough if you are quilting it at home.

If you purchase 3 metres of fabric you have enough for a quilt that is 52" x 74" and that gives you 4" overhang all around (which is enough for most long arm quilters).  This provides for a horizontal seam so if the fabric is directional you will need more.

If you purchase 4 metres of fabric you will have enough for a quilt that is 72" x 74"   and that gives you 4" overhang all around (which is enough for most long arm quilters).

If you purchase 5 metres of fabric you will have enough for a quilt that is 74" x 92"  and that gives you 4" overhang all around (which is enough for most long arm quilters).

If you purchase 7.5 metres of fabric you will have enough for a quilt that is 92" x 118"  and that gives you 4" overhang all around (which is enough for most long arm quilters).  It will have two horizontal seams so if the fabric is directional you will need more.

If you purchase 9 metres of fabric you will have enough for a quilt that is 110" x 118" and that gives you 4" overhang all around (which is enough for most long arm quilters).  It will have two horizontal seams so if the fabric is directional you will need more.

How much Binding do I need?

Assuming that you are cutting straight binding (not bias) and that you are cutting your strips 2.5":

Half a metre will give you 7 strips that will yield 266" of binding.  That will do a quilt that is 67" square or 53" x 80". 

Three quarters of a metre will give you 11 2.5" strips which will yield 418" of binding.  That will do a quilt that is 104" square or 90" x 118".

A full metre of fabric will give you 15 strips which will yield 570" of binding which should be enough for any quilt - as it covers a 142" square!