How the split works
The calculator adds the tax and the tip to the subtotal and divides the total by the number of people. Tip is calculated on the pre-tax subtotal by default, which is what most etiquette guides recommend. Switch it to "No" to tip on the total including tax.
Example
Four friends, a $120 subtotal, $8.40 of tax and a 20% tip. The tip is $24, the total is $152.40, and each person pays $38.10. Rounded up, each pays $39 and the server gets an extra $3.60.
When an even split is not fair
If someone only had a salad and someone else had steak and two drinks, it is fairer to pay for what each person ordered and add the same tip percentage to each. Ask the server for separate checks before ordering when the group is big; many restaurants cannot split after the bill is printed.