How to Calculate TEER Values from Resistance Measurements
This is a step-by-step guide to the TEER formula, blank correction, surface area normalization, and common mistakes to avoid.
Quick Answer: TEER (Ohm·cm²) = (R_sample − R_blank) × Surface Area (cm²). Subtract the blank resistance of your insert and media from your sample reading, then multiply by the membrane surface area in cm².
Trans-epithelial/endothelial electrical resistance (TEER) is one of the most widely used methods for evaluating cell barrier integrity, confluence, and paracellular permeability in in vitro models. While TEER measurements are collected as raw resistance values in ohms (Ω), meaningful comparison across experiments, insert formats, and laboratories requires converting these raw values into standardized TEER units (Ω·cm²).
This guide explains how to accurately calculate TEER values from resistance measurements, including the formula, a worked example, and how to avoid the most common errors.
What Is the Difference Between Resistance and TEER?
When you measure with a TEER instrument, the device reports electrical resistance (Ω) across the cell layer. However, raw resistance values are not directly comparable across experiments because they depend on two physical factors:
- The size of the membrane (surface area)
- The insert or well format used
This means a larger membrane will always appear to have higher resistance, even if the barrier properties are biologically identical to a smaller membrane. TEER solves this problem by normalizing resistance to surface area, producing a value that reflects the intrinsic barrier quality of the cell layer regardless of the insert format used.
What Is the Formula for Calculating TEER?
The standard TEER calculation formula is: TEER (Ω·cm²) = (R_sample − R_blank) × A
Where:
- R_sample = measured resistance with cells present (Ω)
- R_blank = resistance of the insert + membrane + media without cells (Ω)
- A = membrane surface area (cm²)
The result is TEER expressed in ohm-centimeters squared (Ω·cm²), the standard unit for reporting and comparing barrier integrity across experiments.
Step-by-Step TEER Calculation
Step 1: Measure the Blank Resistance
Before seeding cells, measure the electrical resistance of the insert, membrane, and culture media alone. This baseline value is called R_blank. Recording an accurate blank is critical, and skipping this step will result in artificially inflated TEER values.
Step 2: Measure the Sample Resistance
Once your cells have formed a confluent monolayer, measure the resistance of the cell-covered insert under the same conditions used for the blank. This gives you R_sample.
Step 3: Subtract the Blank
Subtract R_blank from R_sample to isolate the resistance contribution of the cell layer itself: Corrected Resistance = R_sample − R_blank
Step 4: Multiply by Surface Area
Multiply the corrected resistance by the membrane surface area (in cm²) to normalize for insert size. This final step converts the raw resistance difference into a standardized TEER value.
TEER Calculation Example
Using a 12-well insert with a surface area of 1.12 cm²:
- R_sample = 1200 Ω
- R_blank = 200 Ω
- Surface area = 1.12 cm²
TEER = (1200 − 200) × 1.12 = 1000 × 1.12 = 1120 Ω·cm²
A TEER of 1120 Ω·cm² is consistent with a well-formed epithelial monolayer in many in vitro barrier models. Always compare your values against established reference ranges for your specific cell type.
Why Do You Normalize TEER by Surface Area?
Different insert formats have different growth areas. Without normalization, resistance values from different insert sizes cannot be compared. A larger membrane physically presents more resistance simply because of its size, not because of stronger barrier function.
Common Transwell®-style insert surface areas are shown below:
| Insert Format | Approx. Surface Area (cm²) | Typical Use |
| 6-well insert | 4.67 cm² | Large-scale assays, Western blot |
| 12-well insert | 1.12 cm² | Standard TEER measurement |
| 24-well insert | 0.33 cm² | High-throughput screening |
| 96-well insert | 0.07 cm² | Automated / high-throughput |
Always confirm the manufacturer-specified surface area for your specific insert. Even inserts in the same well format can vary between suppliers.
How to Interpret Your TEER Results
TEER values vary significantly depending on cell type, culture conditions, and the in vitro model used. There is no universal threshold that applies across all systems. That said, some general reference ranges are widely cited in the literature:
| Barrier Model | Typical TEER (Ω·cm²) | Notes |
| In vivo (rat) BBB | ~5900 | Physiological upper benchmark1 |
| Standard in vitro BBB model | ~100–300 | Primary or immortalized endothelial layers2-3 |
| Advanced iPSC-derived BBB model | up to ~4000 | Retinoic acid enhanced co-culture4 |
| Leaky intestinal epithelium | 50–100 | Small intestine-like permeability5 |
| Caco-2 monolayer (GI) | 150–400 | Widely used drug transport model6 |
| Bronchial ALI culture | 700–1200 | Closest match to in vivo airway barrier7 |
| Calu-3 epithelial monolayer | ~300–600 | Common in vitro lung model8 |
| Alveolar type II epithelial cells | 1000–2000+ | Tight alveolar barrier model9 |
These are some representative TEER values for commonly used barrier models. Data compiled from Srinivasan et al. (2015); measurements commonly performed using WPI EVOM™ systems with STX electrodes and/or EndOhm chambers. More values are shown in the Expected TEER Ranges Application Note.
When interpreting TEER, consider tracking values longitudinally (over time post-seeding) rather than relying on a single time-point measurement. A rising TEER curve that plateaus is often more informative than a single endpoint value.
References
1. Hudson N, Baker FE, Stewart CP, et al. Measurement of transcapillary electrical resistance in live rat brain microvasculature. Microvasc Res. 1992. (Srinivasan Ref 49)
2. Weksler B, Romero IA, Couraud PO. The hCMEC/D3 human BBB model. Fluids Barriers CNS. 2013. (Srinivasan Ref 54)
3. Raub TJ. In vitro BBB endothelial resistance models. In: Pharmaceutical Applications of Cell and Tissue Culture to Drug Transport. Springer. 1990. (Representative in vitro BBB range)
4. Lippmann ES et al. iPSC-derived BBB model with retinoic acid; TEER up to 4000 Ω·cm². Fluids Barriers CNS. 2012. (Srinivasan Ref 53)
5. Anderson JM, Van Itallie CM. Tight junction permeability in GI epithelia. Am J Physiol. 1995. (Srinivasan Ref 74)
6. Hidalgo IJ, Raub TJ, Borchardt RT. Caco-2 as intestinal permeability benchmark. Gastroenterology. 1989. (Srinivasan Ref 32)
7. Ehrhardt C et al. Human tracheal/bronchial ALI TEER 700–1200 measured with EVOM/STX2. Cell Tissue Res. 2002. (Srinivasan Ref 83)
8. Mathias NR et al. Calu-3 TEER 300–600 measured with EVOM/STX2. Pharm Res. 2002. (Srinivasan Ref 96)
9. Horie M et al. Human alveolar type II epithelial TEER 1000– 2000 measured with EVOM. J Toxicol Sci. 2012. (Srinivasan Ref 106)
What Are Common Mistakes When Calculating TEER?
❌ Skipping the Blank Measurement
Failing to measure R_blank before seeding cells is the most common error in TEER workflows. Without subtracting the background resistance of the membrane and media, your calculated TEER will be artificially elevated—and not comparable to any other experiment where blank correction was applied.
❌ Using the Wrong Surface Area
Always verify the membrane surface area from your insert manufacturer's documentation. Do not assume values from memory or from a different supplier's product. Even minor discrepancies in surface area will carry through into your final TEER calculation.
❌ Comparing Raw Resistance Across Experiments
Raw resistance values (Ω) are only valid within a single experimental context. Never compare resistance values across different insert formats, labs, or measurement systems without first converting to normalized TEER (Ω·cm²).
❌ Inconsistent Measurement Conditions
TEER readings are sensitive to temperature, media composition, electrode placement, and equilibration time. Measurements taken with cold media straight from the refrigerator, or with inconsistently positioned electrodes, will introduce variability that has nothing to do with barrier biology. Standardize your protocol and allow media to equilibrate to 37°C before measuring.
❌ Not Equilibrating Media Before Measurement
Beyond temperature, media ionic composition affects conductivity. Using fresh media from a different lot, or media that has been CO₂-equilibrated for different durations, can shift baseline resistance values and confound your results. Use the same media batch and equilibration protocol for blanks and samples alike.
How Modern TEER Systems Improve Data Reliability
The accuracy of any TEER calculation depends directly on the quality of the underlying resistance measurements. Modern TEER instrumentation is designed to reduce the sources of variability described above.
Instruments like the EVOM™ Manual provide stable, low-noise resistance readings and support consistent electrode positioning, helping ensure that your R_sample and R_blank measurements are reliable starting points for calculation.
For higher-throughput workflows, such as compound screening or longitudinal barrier integrity studies, automated systems like the EVOM™ Auto can further streamline TEER data collection by removing manual electrode handling variability and enabling parallel measurements across multiple wells.
Frequently Asked Questions About TEER
What is a good TEER value for a cell monolayer?
It depends on the cell type. Caco-2 intestinal cells typically reach 200–400 Ω·cm² at confluence, while blood-brain barrier models like hCMEC/D3 may read as low as 20–40 Ω·cm². Always compare against published reference ranges specific to your cell line and model system.
Can TEER be calculated without a blank measurement?
Technically yes, but it should never be done in practice. Without blank subtraction, your TEER value includes the resistance of the membrane and media rather than only the cell layer. This inflates results and makes meaningful comparisons impossible. Always measure R_blank before seeding cells.
What units is TEER reported in?
TEER is reported in ohm-centimeters squared (Ω·cm²). Raw instrument readings are in ohms (Ω). The conversion to Ω·cm² is what allows comparison across different insert formats and experimental systems.
What is the difference between TEER and resistance?
Resistance (Ω) is the raw electrical measurement from the instrument and depends on both barrier quality and the physical size of the membrane. TEER (Ω·cm²) normalizes resistance to membrane area, making it a size-independent measure of barrier integrity that can be compared across formats and laboratories.
Which instruments are used to measure TEER?
The most common instruments for measuring TEER in in vitro cell culture are voltohmmeter-based systems such as the EVOM™ series (World Precision Instruments), chopstick electrodes for manual measurement, and automated TEER platforms designed for multi-well formats. The choice of instrument affects electrode placement consistency and measurement reproducibility.
How often should TEER be measured?
Measurement frequency depends on your experimental design. For barrier formation studies, daily measurements from seeding to confluence are common. For endpoint assays, a single pre- and post-treatment measurement may suffice. Longitudinal monitoring typically provides more interpretable data than a single time-point reading.
Summary
Accurate TEER calculation requires three things: a reliable blank measurement, the correct membrane surface area, and consistent measurement conditions. The formula is straightforward, but the quality of your result depends entirely on the discipline applied at each step.
- TEER normalizes resistance to membrane surface area (Ω·cm²)
- Always subtract R_blank before applying the formula
- Use the manufacturer-confirmed surface area for your specific insert
- Standardize temperature, media, and electrode placement across all measurements
- Report results in Ω·cm² for meaningful cross-experiment comparison
Accurate TEER calculation is foundational to interpreting barrier function data, and to generating results that can be trusted, reproduced, and published with confidence.
