Insect trap count calculator: catch per trap per day, flight peaks and thresholds (free)

Paste insect trap checks (date, site, traps, count) and get catch per trap per day, a moving average, flight peaks, site and week comparisons and flags at a threshold you set. Runs in your browser.

Keep it one tap away for everyday use.

Paste checks
Per trap-day
Peaks
Flags

Nothing is uploadedWorks offline once open

Trap checks

Date, site, number of traps, insects caught, and (optional) days the traps were out. One check per row. A header row naming the columns lets them come in any order.

The example is a made-up season of weekly pheromone-trap checks in two orchards; in mid-June one North trap was lost, so that week has 2 traps.

Index Days before the first check Moving average Flag at or above (index) Peak must reach (% of top) Dates like 04/05/2026 are

The index is catch ÷ (traps × days out), so checks with lost traps or longer gaps compare fairly. Days come from the days column if there is one, else from the gap since the site's previous check; the first check of each site uses days before the first check. The moving average is centred on each check and smooths week-to-week noise. A flight peak is a check where the smoothed index is higher than at the checks either side and at least the share of the site's top you set. The flag level is yours to choose (for example an action threshold from your local advisory service); the 5 on the page is only an example.

Population index

Sites compared

Season index = total catch ÷ total trap-days, so long or busy checks count for more; the mean of checks gives every check the same weight.

Week by week

Every check

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What it does

Pheromone traps, light traps, sticky cards and pitfall traps are checked again and again through a season, but raw counts are hard to compare: a trap left out for ten days catches more than one left out for seven, and a site with four traps catches more than a site with two. This tool turns trap checks into a population index, the catch per trap per day (or per night, or per week), so every check, site and week can be compared fairly. It smooths the series, finds the flight peaks, compares sites and weeks side by side, and flags checks at or above a level you choose. Everything is worked out in your browser.

How to use it

Paste one row per check: date, site, traps, count, and optionally days the traps were out. With a header row naming the columns they can be in any order. Three columns (date, traps, count) are read as one site. You can also open a CSV or Excel file.
Pick the index unit and the other options below. The page updates as you type.
Download the checks or the week table as CSV, or the full report as an image, PDF or Word file.

What each option does

Index: catch ÷ (traps × days). “Per trap per night” is the same number with a different label, for light traps; “per trap per week” multiplies by 7.
Days before the first check: when there is no days column, the days for each check are the gap since that site’s previous check, and the first check uses this number.
Moving average: the mean of the index over 3 or 5 checks centred on each check, which evens out weather and counting noise.
Flag at or above: checks whose index reaches this level are flagged. The 5 on the page is only an example; use the action threshold for your pest and crop from your local advisory service, and check the official source.
Peak must reach: a flight peak is a check where the smoothed index is higher than the check before, at least as high as the check after, and at least this share of the site’s highest smoothed value. Raise it to ignore small bumps.

Worked example

The made-up example has 14 weekly checks in two orchards, three traps in North (two in mid-June after one was lost) and two in South. The season index is 3.98 insects per trap per day in North and 2.89 in South. North’s highest check is 9.67 on 29 June, and the 3-check moving average shows two flights, peaking on 25 May and 29 June; South’s flights peak on 26 May and 14 July. With the example flag level of 5, North is first flagged on 25 May and South on 26 May, with four flagged checks each. The mid-June North check caught 62 insects in 2 traps over 7 days, an index of 4.43; without the correction for the lost trap it would look like a drop.

Tips

Count every check, including zeros: a missing zero makes the next gap longer and lowers that check’s index.
Use the same trap type and lure across sites, or the index compares lures rather than populations.
The week table pools all checks dated in the same ISO week, which helps when sites are checked on different days.

Frequently asked questions

Why is the season index different from the mean of checks? The season index pools all insects over all trap-days, so long checks and checks with more traps weigh more. The mean of checks treats every check equally.

Can I use it for several species? Run each species separately, or put the species in the site name (for example “North, moth A”).

Is my data sent anywhere? No. It stays in your browser, and the page works offline once loaded.

Where the numbers come from

Catch per unit effort (catch per trap per day) and centred moving averages: standard monitoring arithmetic, as described in general entomology and pest-monitoring texts.
ISO 8601 week numbers.
Checked against an independent pandas implementation (date gaps, rolling centred means, ISO weeks) on the page's example.

Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.

Last updated 2026-11-09.