Free · Measurement and planning

Shared Bill Gratuity and Total

Calculate gratuity, total bill and equal per-person shares, or solve a missing bill, rate or share.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

For the worked example, tip_amount = 20.00000000, total = 120.0000000, tip_per_person = 5.000000000, total_per_person = 30.00000000.

Tip = bill × tip rate; each share = total / people.

Worked example

Enter these known values and leave the other values blank.

Bill
100 USD
Tip
20 %
Number of people
4
Tip amount
20 USD
Total
120 USD
Tip per person
5 USD
Total per person
30 USD

Assumptions and limitations

  • Split equally among a positive whole number of people. Enter any taxes already included in the bill.
  • Currency selectors label amounts; they do not convert exchange rates.
  • Results follow the stated ideal arithmetic model. Display rounding does not change the underlying calculation.
  • Supply sufficient known values and leave the desired quantity blank. Controls retain captured inverse branches and units.
  • If a retained lock prevents a reverse calculation, unlock the quantity you want to solve before supplying the known values.

Common questions

What does the worked example demonstrate?

Tip = bill × tip rate; each share = total / people.

Can I change the measurement units?

Available selectors convert the entered physical quantity. Use compatible units for all related quantities.

Why can a result be blank?

A missing input, invalid denominator or underdetermined relationship cannot provide a unique finite result.

References

Use exact-sign physical domains, exact discrete counts where applicable, and documented model bounds. Source arithmetic is preserved. Integer membership is checked with isInteger, so ordinary, tiny and large fractional counts are rejected even when tolerant floor equality would pass.

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