Since other licencing areas will employ different tariffs, and this tariff is unique to the Scottish Borders licencing area, this Google Maps powered taxi fare calculator is only intended for use with Scottish Borders licenced taxis.
As with any tool of this nature it can only give a guide, but if you give it adequate information it will certainly be close regarding distance. It can not however factor in waiting time and only the final meter reading will determine the actual fare.
This taxi fare calculator is only relevant to social hours travel for up to four passengers. For five to eight passengers add fifty percent. Unsocial hours, 10pm to 6am cost an additional 25 percent which ever tariff is effective.