Enter the profits before the damaging event and the profits after the damaging event into the calculator to determine the lost profits.

Lost Profits Calculator

Enter any 2 values to calculate the missing variable

How to Calculate Lost Profits

The calculator uses a simple before-and-after method: compare profit before the incident with profit after the incident using the same time window and comparable operating conditions. ([calculator.academy](https://calculator.academy/lost-profits-calculator/))

LP = PB - PA
Input Meaning How to Enter It
Profits Before Incident (PB) Profit earned during a normal comparison period before the damaging event Use profit, not revenue, for the same number of days, weeks, or months you plan to compare
Profits After Incident (PA) Profit earned during the matching period after the event Use the same accounting method, business unit, and time length as PB
Lost Profits (LP) The decrease in profit attributed to the incident The calculator returns this automatically

How to Use the Calculator Correctly

  1. Choose a comparison period, such as 7 days, 30 days, or 1 quarter.
  2. Enter profit from a normal period before the incident.
  3. Enter profit from the matching period after the incident.
  4. Review the result and confirm that both periods are truly comparable.
Check Why It Matters
Same time length A 10-day post-incident period should be compared to a 10-day baseline, not to a month or quarter
Same season or demand level Busy-season profits and slow-season profits are usually not directly comparable
Same accounting basis Mixing gross profit, net profit, cash flow, or revenue will distort the result
Same business scope Compare the same location, product line, or operating segment where possible

Reading the Result

Result Interpretation
Positive value Profit fell after the incident, indicating lost profits for the selected period
Zero No measurable profit change between the two periods
Negative value Profit after the incident exceeded the baseline, so there is no loss under this comparison

Example Scenarios

Before Incident After Incident Lost Profits Meaning
$18,000 $11,500 $6,500 The business earned $6,500 less profit during the comparison period
$42,000 $42,000 $0 No profit loss appears for that period
$25,000 $27,500 -$2,500 Post-incident profit was higher than the baseline

Common Mistakes

Mistake Why It Causes Problems Better Approach
Using revenue instead of profit Revenue ignores costs and can overstate the loss Use the same profit measure for both periods
Comparing different time spans A longer baseline usually inflates the apparent loss Match the exact period length
Ignoring seasonality Normal fluctuations may be mistaken for damages Use a comparable historical period
Changing the expense treatment Different profit definitions make the comparison unreliable Keep the accounting method consistent

When This Method Works Best

This calculator is most useful when you have a clear pre-incident baseline and a matching post-incident period. It is especially practical for short-term interruptions, sudden performance drops, and situations where the business had relatively stable operations before the event. The page’s method is specifically the before-and-after approach. ([calculator.academy](https://calculator.academy/lost-profits-calculator/))

Important Context

Lost profits typically refer to profit that a person or business would have earned but for a damaging event. In legal or claims settings, recovery often depends on the facts, causation, reasonable support for the calculation, mitigation efforts, and the rules of the applicable jurisdiction. ([calculator.academy](https://calculator.academy/lost-profits-calculator/))

Quick FAQ

Question Answer
Should I use gross profit or net profit? Use whichever profit measure is appropriate for your analysis, but keep it consistent for both periods.
Can I compare different months? You can, but the result is more reliable when the months have similar demand patterns, pricing, and operating conditions.
What if the business was already trending up or down? A simple before-and-after comparison may be too basic; you may need a more tailored baseline outside this calculator.