What Is the Countess 3?
The Thermo Fisher Countess 3 is a benchtop automated cell counter designed for routine cell culture. It replaces manual haemocytometer counting with a touchscreen-driven, slide-based system that reports total cell count, viability and average cell size in under 10 seconds per sample.
UK labs typically consider the Countess 3 when throughput is too high for a haemocytometer but lower than a high-end flow cytometry or image cytometry system. It sits alongside alternatives such as the LUNA-II, EVE Plus and CellDrop in the mid-range automated cell counter market.
This review covers how the Countess 3 works, what it tiers in the UK, its strengths and limitations, and how it compares to the Countess 3 FL. We do not sell cell counters; we compare them so you can request the right demonstration and quote from an authorised distributor.
Quick (, estimated):
- Countess 3: a depending on slides, warranty and bundle
- Countess 3 FL: roughly a premium over the base unit
- Disposable precision slides: sold in packs; reusable counting chambers also available
Countess 3 Specifications
| Feature | Countess 3 | Countess 3 FL |
|---|
| Detection method | Brightfield + trypan blue | Brightfield + GFP/RFP fluorescence |
| Typical count time | < 10 seconds | < 10 seconds |
| Sample volume per slide | 10 µL | 10 µL |
| Display | 7-inch touchscreen | 7-inch touchscreen |
| Cell size range | 4 – 70 µm | 4 – 70 µm |
| Results saved | USB export, CSV + annotated images | USB export, CSV + annotated images |
| Fluorescence channels | None | GFP (EX 470/EM 510), RFP (EX 530/EM 590) |
| Typical UK tier | Entry | Entry |
| Typical UK lead time | 2–4 weeks | 2–4 weeks |
What We Like About the Countess 3
- Speed: a 10-second count is a genuine time-saver over manual haemocytometers.
- Ease of use: The touchscreen interface is straightforward and stores counting profiles for repeat experiments.
- Data export: Annotated images and CSV files export to USB for lab notebooks and LIMS uploads.
- Proven optics: Autofocus and de-clustering algorithms are consistent with earlier Countess models familiar to many UK labs.
- Upgrade path: If fluorescence needs appear later, the Countess 3 FL adds GFP and RFP without changing the whole workflow.
Limitations to Consider
- Consumable outlay: Disposable precision slides add ongoing outlay; reusable chambers reduce this but need cleaning validation.
- Single-sample throughput: The Countess 3 counts one slide at a time. High-throughput labs may prefer a multi-sample image cytometer.
- No fluorescence on base model: GFP/RFP viability or transfection assays require the FL upgrade.
- Limited cell size extremes: Very small bacteria or very large spheroids sit outside the standard 4–70 µm range.
Countess 3 vs Countess 3 FL: Which Should UK Labs Choose?
Choose the standard Countess 3 if your lab only needs brightfield trypan blue viability for routine cell culture. It handles the vast majority of suspension and adherent cell lines used in UK research.
Choose the Countess 3 FL if you also need fluorescence-based viability, transfection efficiency or apoptosis assays. The GFP and RFP channels let you count fluorescent cells without secondary dyes, which can be useful for lentivirus or CRISPR reporter work.
For a broader comparison of automated cell counters in the UK, see the Best Automated Cell Counter UK 2026 guide.
Best Use Cases for the Countess 3
| Use case | Countess 3 suitability |
|---|
| Routine cell culture passaging | Excellent — fast viability and density checks |
| Cell seeding for assays | Excellent — consistent counts improve reproducibility |
| Transfection efficiency | Requires Countess 3 FL or an alternative with fluorescence |
| High-throughput screening | Limited — consider multi-sample image cytometer |
| Primary cell viability | Good — trypan blue works for many primary isolates |
| Bacterial or very small cells | Not ideal — size range and resolution limitations |
UK Demo, Quote and Stock Guidance
The Countess 3 is distributed in the UK by Thermo Fisher Scientific and authorised resellers. Standard configurations are usually available within 2–4 weeks; custom slide bundles or extended warranties may add time. Always ask whether the quoted tier covers installation and any starter slide packs.
Frequently Asked Questions
What is the Countess 3 UK tier level?
Expect premium-tier pricing depending on configuration, slide bundles and warranty. The Countess 3 FL tiers roughly a more.
What is the difference between Countess 3 and Countess 3 FL?
The standard model uses brightfield and trypan blue. The FL model adds GFP and RFP fluorescence for transfection and fluorescence viability assays.
How fast is Countess 3 counting?
Most counts finish in under 10 seconds per sample, with immediate viability and size data on the touchscreen.
Where can UK labs request a demo?
Contact Thermo Fisher Scientific UK or an authorised distributor for a demonstration and official quotation.
What are the main alternatives?
LUNA-II, EVE Plus, CellDrop and Countess 3 FL are the most common alternatives in UK research labs.