FIELD TOOL / OBSERVATION MATH
Make your trap
counts comparable.
Calculate captures per trap-night and compare two periods. Keep the sampling effort visible alongside the count.
Your monitoring record
Use the same identified pest and count only new captures. Every trap in a period must have been usable for all the nights entered. For mixed durations, calculate each stable group separately.
Your capture summary
| Period | Captures | Traps | Nights | Trap-nights | Captures / trap-night |
|---|
This is a descriptive record, not an infestation estimate, eradication confirmation, or treatment recommendation. A zero catch is not proof of absence.
METHOD / LIMITS
How the calculation works
Trap-nights = active traps × usable nights. Capture rate = new captures ÷ trap-nights. When the setups are comparable and the first rate is greater than zero, percentage change = (second rate ÷ first rate − 1) × 100. Displayed rates are rounded to three decimal places; the comparison uses unrounded values.
This is our arithmetic summary of a monitoring record. It has not been validated as a diagnostic model. Do not pool different species, lure types, rooms with changed placements, or live sightings with trap captures. Keep dates, location labels, and any cleaning or management actions in your separate notes.
UC IPM's cockroach guidance supports numbered traps and records of catches by location. It does not endorse this calculator or provide a universal action threshold. Colorado State University's moth guidance distinguishes monitoring from control.
Use the record with the right guide
- Saw one cockroach at night? What to check next
- What pantry moth trap catches tell you
- Silverfish in the bathroom: a practical checklist
- Print a repeat-observation worksheet
Common questions
What is a trap-night?
One functioning trap deployed for one night is one trap-night. Two functioning traps over seven nights provide 14 trap-nights. Only include time the devices were usable.
Does a lower capture rate prove treatment worked?
No. The rate summarizes observed catches and effort. Placement, trap type, lure condition, pest behavior, and other changes affect catches. This tool provides no treatment threshold or statistical significance test.
What if a trap stopped working or was moved?
Split the observation into periods with a stable setup. Do not enter a full week for a device that was missing or unusable for part of it. Use the evidence log to retain individual device records.
Are my numbers saved or uploaded?
The calculation runs in this page. Input values are not saved or submitted by this tool. Print the summary before leaving if you want to keep it.