A percentage-based gas calculator in Google Sheets can handle both the math and the paper trail. Put each fill-up on its own row, multiply the total by each person's agreed share, then compare those shares with the amount each person actually paid.
That distinction prevents the most common mistake. The person holding the card may have fronted $150, but that doesn't make their final share $150. With 40%, 30%, 20%, and 10% shares, the obligations are $60, $45, $30, and $15.
Turns out, the spreadsheet is the easy part. Your group needs a clear rule for who shares each fill-up, when percentages change, and when a reimbursement counts as settled.
Choose the split rule before the first fill-up
A percentage is a math format, not a fairness rule. Agree on what the percentages represent before anyone starts entering receipts.
| Split method | Fits when | Record in the sheet |
|---|---|---|
| Equal split | Everyone rides the same route together | The same percentage for each person |
| Usage-based split | People join or leave during different legs | The riders or mileage covered for that row |
| Income-based split | The group wants contributions to reflect agreed income proportions | The final percentages, not anyone's salary |
| Custom split | A driver, sponsor, or participant has a special arrangement | The rule in the Notes column |
Income-based shares deserve a privacy check. The sheet only needs the agreed result, so don't add salaries or other personal financial details unless everyone has a clear reason to see them.
A late joiner can have a different percentage on later rows. Don't rewrite earlier fill-ups just to make the whole trip look uniform.
Build the Gas Log tab
Start with a blank Google Sheet and create a tab called Gas Log. Use one row per fuel purchase, even if the same person pays several times.
The layout below supports four people. Replace Person 1 and the other placeholders with names.
| Column | Header | What to enter |
|---|---|---|
| A | Date | Date of the purchase |
| B | Paid by | Person who covered that receipt |
| C | Odometer start | Reading at the beginning of the segment |
| D | Odometer end | Reading at the end of the segment |
| E | Total miles | Formula using the two odometer readings |
| F | Gallons | Gallons purchased, if shown on the receipt |
| G | Total cost | Full receipt amount |
| H | Split type | Shared or Reimbursement |
| I | Person 1 % | Agreed percentage for that person |
| J | Person 1 share | Formula for that person's dollar share |
| K | Person 2 % | Agreed percentage for that person |
| L | Person 2 share | Formula for that person's dollar share |
| M | Person 3 % | Agreed percentage for that person |
| N | Person 3 share | Formula for that person's dollar share |
| O | Person 4 % | Agreed percentage for that person |
| P | Person 4 share | Formula for that person's dollar share |
| Q | Split check | Sum of the percentage cells |
| R | Reimbursed? | No, Partial, or Yes |
| S | Receipt or notes | Receipt link, participant note, or exception |
The Paid by column and the percentage columns serve different purposes. Paid by shows who advanced the money; the percentages show who should ultimately bear the cost.
Use Split type = Reimbursement when one person paid upfront and expects repayment. Keep the agreed shares in place. Entering 100% for the payer and 0% for everyone else is appropriate only when that payer is actually covering the entire cost, not when the group plans to reimburse them.
Add the Google Sheets formulas
Enter the formulas in row 2, then copy them down as new fill-ups are added.
| Cell | Formula | Result |
|---|---|---|
| E2 | =IF(OR(C2="",D2=""),"",D2-C2) |
Calculates miles for the segment |
| J2 | =IF(OR($G2="",I2=""),"",$G2*I2) |
Calculates Person 1's share |
| L2 | =IF(OR($G2="",K2=""),"",$G2*K2) |
Calculates Person 2's share |
| N2 | =IF(OR($G2="",M2=""),"",$G2*M2) |
Calculates Person 3's share |
| P2 | =IF(OR($G2="",O2=""),"",$G2*O2) |
Calculates Person 4's share |
| Q2 | =IF($G2="","",SUM(I2,K2,M2,O2)) |
Checks the row's percentage total |
For a 40% share, type 40%, not 40. Format the percentage cells as Percent, the cost and share columns as Currency, and the odometer columns as Number.
Review the Split check column before settling anything. Every completed cost row should show 100%. A blank row can remain blank.
You can add data validation to the percentage columns so entries stay between 0% and 100%. A valid range alone doesn't prove that the row totals 100%, which is why the separate check column matters.
Create a summary for reimbursements
Add a second tab named Summary. This tab turns individual fill-ups into a balance for each person.
Set up four columns:
| Column | Header | Purpose |
|---|---|---|
| A | Person | Name matching the Paid by entries |
| B | Total paid | Receipts that person covered |
| C | Total share | Their calculated responsibility |
| D | Net balance | Total paid minus total share |
For the first person in A2, use these formulas:
B2:=SUMIF('Gas Log'!$B$2:$B$100,A2,'Gas Log'!$G$2:$G$100)C2for Person 1:=SUM('Gas Log'!$J$2:$J$100)D2:=B2-C2
For Person 2, change the share range in C2 to column L. Use column N for Person 3 and column P for Person 4. Keep the names in column A consistent with the Paid by entries, including spelling.
A positive net balance means the person paid more than their share and should receive money. A negative balance means they owe money.
For example, if Alex pays the full $150 receipt and the shares are 40%, 30%, 20%, and 10%, the summary looks like this:
| Person | Total paid | Total share | Net balance |
|---|---|---|---|
| Alex | $150.00 | $60.00 | +$90.00 |
| Blair | $0.00 | $45.00 | -$45.00 |
| Casey | $0.00 | $30.00 | -$30.00 |
| Drew | $0.00 | $15.00 | -$15.00 |
The group can settle those balances by cash, a payment app, or another agreed method. The sheet tracks the obligation; it doesn't move money or confirm that a payment arrived.
If people pay in installments, add a Settlements tab with Date, From, To, Amount, Status, and Note columns. A reimbursement is not a new gas expense. Record it as a settlement, then update the gas row from No to Partial or Yes.
Use the sheet at each gas stop
- Before the trip, replace the placeholder names and agree on the split rule. Enter 0% for anyone who is intentionally excluded from a particular fill-up.
- At each stop, save the receipt and record the date, payer, cost, gallons, and odometer readings.
- Enter that row's percentages. Check that the Split check column shows 100%.
- Review the calculated shares and confirm that the receipt amount matches the Total cost cell.
- At the end of the day or trip, review the Summary tab and record actual repayments on the Settlements tab.
- Mark a row as
Yesonly after the relevant reimbursement has been made. UsePartialwhen money is still outstanding.
Use a separate row if one receipt was divided between two cards. Give both rows the same date and receipt note, then enter the amount paid by each person. A single Paid by cell shouldn't contain an ambiguous list of names.
Share carefully and protect the formulas
Share the sheet after testing one sample row. Google Sheets can show edits to people with access, but everyone doesn't need editing permission.
| Access setting | Suitable for |
|---|---|
| Editor | People entering receipts or updating settlement status |
| Viewer | People who only need to review totals |
| Protected range | Formula columns and summary cells that shouldn't be overwritten |
To be honest, giving everyone Editor access is convenient but unnecessary for a group that only needs to check balances. Protect the formula columns, and check the permissions on any linked receipt folder separately.
Most errors are easy to catch:
| Problem | Fix |
|---|---|
| Percentages don't total 100% | Correct the row before using its balance |
| Payer is confused with final responsibility | Keep Paid by separate from percentage shares |
| A formula was overwritten | Restore it from the row above and protect the range |
| A reimbursement is entered as a gas expense | Record it on Settlements instead |
| A percentage rule changed mid-trip | Apply the new rule only to the relevant rows and explain it in Notes |
| A receipt is missing | Add a photo or digital receipt link while the details are fresh |
Keep the sheet readable. Long notes can explain exceptions without changing the arithmetic.
Keep records and separate tax questions
Export a copy of the sheet as a PDF or CSV if the group wants a trip record. Keep the receipts with it, especially when one person paid several costs for everyone else.
According to the IRS announcement, the 2026 federal business standard mileage rate is 72.5 cents per mile. That rate applies to qualifying business use; it isn't a suggested formula for splitting gas on a personal road trip.
Actual vehicle costs can be another method where applicable, and the treatment depends on the tax situation and supporting records. Personal gas reimbursements between friends or family typically aren't deductible simply because they appear in a spreadsheet. State rules, employer policies, and individual facts can differ, so ask a qualified tax professional about a business-use question.
The mileage rate is not a gas price, a reimbursement requirement, or a fairness rule. Keep tax records separate from the group's informal agreement.
Common questions
Can I use income percentages without listing salaries?
Yes. Agree on the percentages privately and enter only the final figures in the sheet. That keeps the calculation useful without exposing the income information behind it.
What if one person pays for the entire fill-up?
Enter that person in Paid by, record the full receipt in Total cost, and keep the agreed shares in the percentage columns. The Summary tab will show what the payer should receive after accounting for their own share.
What if someone joins for only part of the trip?
Use a different percentage on the rows covering that person's participation. Add a note naming the participants or segment so nobody has to reconstruct the decision later.
Does the calculator send reimbursement requests?
No. It calculates shares and net balances. You can use those figures to request payment through a method your group already accepts, then record the result in the settlement log.
Create the Gas Log and Summary tabs first. Enter the $150 sample row, confirm the Split check shows 100%, and verify that the Summary balances net to zero before you clear the sample and log the first real fill-up.