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I bought a 2007 toyota Estima 57,000km on the clock. When I am doing 100 KPH cars are zooming by me. I tested it using the car GPS and my phone GPS as well as matching the speed of a 2013 bwm with cruise control.

So to get to 100 KPH I have to do 112 or 113kph on my speedo. Everything on the car is 100% factory standard and the tires are correctly filled and the tread is in good condition.

Is there a legal tolerance that dealers selling cars have to abide by that the speedometer has to be accurate by? Considering I am being abused by other motorists as I generally drive slightly under the speed limit anyway it was a huge relief to find out why I was being abused. The faster I go the higher to inaccuracy. When I'm going 40kph it is out by 6k.

Should the dealer sort the calibration out or is this kind of thing acceptable. I have never driven a car with such an inaccuracy in it.

Generally speaking, most speedometers are more accurate than this - with most modern cars over-reading by around 6% to 8%. However, speedos are governed by an International standard (UN ECE regulation 309/00), which is calculated using a seemingly complicated formula. However, once you understand the formula it isn't all that complicated.
The formula states 0 ? (V1 - V2) ? 0.1 V2 + 4 km/h (where V1 is the displayed speed and V2 is the actual speed).
Without getting too bogged down in mathematics, this means that a speedo reading of up to 114km/h at 100km/h is within tolerance. However, the 6km/h that your speedo is misreading at 40km/h would be out of tolerance.
In the first instance, the best advice is th make sure your calculations are correct.
I'd suggest approaching the dealer and having someone like Robinson Instruments conduct an inspection. If the speedo is outside of allowable tolerance, the dealer should pay for the repair.