Typed a wrong number mid-calculation? Fix it without starting over
Short answer: You can only fix one entry if your calculator kept the entries. Use a tape calculator: every number is a separate line, so you tap the wrong line, correct the amount, and the total recalculates. No retyping the whole list.
Why you usually have to start over
A standard calculator turns 45 + 120 + 38 into a single number. Once you press +, the 120 is gone. If you typed 210 instead of 120, the only fix is to subtract 210, add 120, and hope you remembered correctly, or clear and retype everything.
1. Find the wrong line
Scroll the tape and compare it with your receipts or list, top to bottom. Memos help: if each line says "gas", "lunch", "parking", matching a line to its source takes a second. A few quick checks:
- Total off by a round 9, 90 or 900? Two digits were probably swapped (120 vs 210).
- Off by exactly one amount? That line was entered twice or skipped.
- Off by double an amount? It was added instead of subtracted.
2. Correct the amount or the sign
In Sumroll, tap the line to open it, change the amount or switch + to −, and save. Every subtotal and total below it recalculates at once, and the edited line is highlighted so you can see what changed.
3. Insert a line you missed
Forgot a receipt in the middle? Open the line where it belongs and choose insert above. The new line goes in the right place and the totals below it update.
4. Delete a duplicate
Swipe a line to delete it. If you removed the wrong one, tap undo.
5. Check the result once
Read the tape top to bottom one last time. Because every entry is still there, checking takes seconds, and you can share the corrected tape as text or CSV.
FAQ
Why can't I edit an earlier number on my phone calculator?
A standard calculator only stores the current result, not the list of entries that produced it. There is no line to go back to.
I edited a line but the total did not change. Why?
Some tape apps keep the old total after an edit. In Sumroll every subtotal and total below the edited line recalculates immediately, and the changed line is highlighted.
How do I spot which number is wrong?
Compare the tape against your source line by line, and use memos so each figure is easy to match to its receipt. A total that is off by exactly double one amount usually means that amount was entered twice.