How accurate is the ROI extrapolation?

Reasonable for plates that are evenly populated. The ROI method assumes uniform spatial distribution, which is good for L4-young adult plates but breaks down for plates with strong food-edge effects or for mixed-stage populations where worms cluster on the lawn edge.

What density triggers a starvation warning?

Above 200 worms/$\text{cm}^{2}$ (the "crowded" category) the OP50 lawn typically depletes within 24 hours and the population enters dauer formation. The calculator flags this with a warning so you can chunk to a fresh plate before the crash.

Why subtract a 10% rim from the plate area?

The outer ~10% of any NGM plate dries faster than the center and rarely supports worms. The usable area for population estimates is the inner ~90% — for a 60 mm plate, that's about 25.4 $\text{cm}^{2}$ instead of the full 28.3 $\text{cm}^{2}$.

Can I use this for mixed-stage plates?

Yes, but the total count will include eggs, L1s, and adults indiscriminately. If you need stage-specific counts, score a smaller ROI under the dissecting scope and use the bleach synchronization calculator to set up an age-matched cohort.

How does this connect to OP50 prep?

The total population estimate tells you how soon the lawn will be depleted. A 60 mm plate seeded with 100 µL OP50 supports about 3,000 worms before depletion, so a "normal" density plate (~3,200 worms) is at the chunking threshold.

ToolsConductScience tool

C. elegans StrainsFree in-browser calculator

C. elegans Plate Population Counter.

Estimate total worms per plate from a visual density preset or an ROI count, and classify plate density against the WormBook starvation threshold.

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Validated2026-04-06

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Load example celegans plate counter data to see the full workflow

Plate Inputs

Plate size

Counting method

Visual density

Estimated Population

Density

125

worms/cm²

Total worms

3,175

on plate

Plate area

25.4 cm²

60mm usable

Density category

normal

When to use

Routine plate density checks during stock maintenance
Estimating worm count for a bleach synchronization
Onboarding new lab members to plate scoring
Planning chunking and OP50 prep schedules
Comparing density across plates in a stock collection

Do not use for

For stage-specific counts (use a picking-based method)
For lifespan or brood size assays where individual count matters
For plates with strong spatial heterogeneity (use multiple ROIs and average)

Always score the worm-rich center, not the dry rim

The outer ~10% of any NGM plate is too dry to support worms. ROIs taken from the rim will always undercount. Choose ROIs from the center of the lawn.

Score before chunking, not after

A plate that looks crowded after a 5-day passage may already be in mass dauer. Score on day 3 and chunk if density is approaching 200 worms/ $\text{cm}^{2}$ .

Use the same magnification for all scoring

Density estimates depend on what you can resolve. A 1 $\text{cm}^{2}$ ROI at 20× magnification undercounts L1s. Standardize on 40× for routine scoring.

Document any dauer-rich plates

Mass dauer formation is a red flag for chronic stress (food, temperature, contamination). Score and document any plate with > 30% dauers and investigate the cause before discarding.

Method

Plate area = $\pi$ $\times$ (d/2)² $\times$ 0.9 (excludes outer dry rim). For preset density: midpoint of category $\times$ area. For ROI: count / ROI area $\times$ plate area. Density classification: <50 sparse, 50–200 normal, >200 crowded. Crowded plates and >5,000 total worms trigger warnings.

Validated

Last validated 2026-04-06. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.

How to cite

How to Cite

ConductScience C. elegans Plate Population Counter (v0.96.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/celegans-plate-counter

Stiernagle T. Maintenance of C. elegans. WormBook. 2006. doi/10.1895/wormbook.1.101.1

Brenner S. The genetics of Caenorhabditis elegans. Genetics. 1974;77(1):71-94.

C. elegans Plate Counting Methods

Visual density preset

Look at the plate under the dissecting scope and pick sparse, normal, or crowded. Fastest method, accurate to ±50% — good for routine maintenance decisions and stock chunking schedules.

Region-of-interest (ROI) count

Count worms in a defined area (typically a 1 $\text{cm}^{2}$ square drawn on the plate bottom with a marker) and multiply by the total plate area. Accurate to ±20% for evenly populated plates.

Picking-based count

For high-precision experiments (lifespan, brood size), pick worms one by one to a count-only plate. Slow but exact. Use for any experiment where worm count matters at the individual level.

WormSizer / WormLab automated count

For high-throughput labs, image analysis software counts worms from plate scans. The accuracy is comparable to ROI counts but lets you process hundreds of plates per day.

Managing Plate Density

Plate density management is the single biggest determinant of stock health in C. elegans labs.

Why density matters

Above ~200 worms/ $\text{cm}^{2}$ , the OP50 lawn cannot keep up with metabolic demand. Worms enter starvation, which triggers dauer formation in many strains. Once a plate goes into mass dauer, the cohort is unusable for most assays and the only recovery is to chunk the few non-dauer worms and re-establish.

Standard maintenance density

Aim for ~100 worms/ $\text{cm}^{2}$ as a maintenance target. This gives 2–3 days of buffer before food depletion and produces enough progeny for the next chunk.

Chunking strategy

Cut a 1 $\text{cm}^{2}$ agar block from the densest part of the plate and transfer it to a fresh seeded plate. The worms migrate onto the new lawn within hours. Repeat every 2–3 days at 20 °C for active stocks, every 5–7 days at 15 °C for slower turnover.

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