Guides
How tip splits, margin vs markup, and percentages are calculated.
How a tip calculator splits a bill
Tip amount, total, and per-person rounding — the same math CalcKit uses.
Margin vs markup
Why 25% margin is not 25% markup, and how sell price is derived from cost.
Three percentage problems
X% of Y, “what percent is X of Y”, and percent change — including zero and negatives.
FAQ
A few common questions.