How To Get The Tax Rate From A Product

I am looking to get the tax rate value from a product (not quote item) in a plugin, which fires on the beforeAddProduct() method.

Currently I have the following in my plugin code:

$taxClassId = $product->getTaxClassId();

this returns an id such as 2 for example.

I attempt to use this value using the MagentoTaxApiTaxCalculationInterface getCalculatedRate() method:

$productTaxRate = $this->taxCalculation->getCalculatedRate($taxClassid);

but then this just returns a 0 which is incorrect as in the admin, the Tax Class is set to A_GEN_STANDARD which is set to a rate of 20%

Surely there must be a simple to get the tax rate value from a product?

Just to confirm, this is for a product, not a quote item 🙂

Thanks everyone