ASUS ROG Strix XG309CM vs LG UltraFine 40U990A-W
Side-by-side comparison of viewing distance, PPI, and specifications
Category Ranking
Pixel Density (PPI)67in category
ASUS ROG Strix XG309CM94 PPI #65
LG UltraFine 40U990A-W140 PPI #30
93 PPI224 PPI
HDR Peak Brightness67in category
ASUS ROG Strix XG309CM300 nits #65
LG UltraFine 40U990A-W600 nits #22
250 nits2000 nits
DCI-P3 Color Gamut
LG UltraFine 40U990A-W99% #2
79%100%
Refresh Rate
ASUS ROG Strix XG309CM220 Hz
LG UltraFine 40U990A-W120 Hz
StandardHighUltra
Summary
- Sharpness: advantage LG UltraFine 40U990A-W — At 65cm, the LG UltraFine 40U990A-W is retina (140 PPI) while the ASUS ROG Strix XG309CM is not — you need to sit at least 93cm away for pixel-free viewing.
- Brightness: advantage LG UltraFine 40U990A-W — The LG UltraFine 40U990A-W is 50% brighter in SDR (450 vs 300 nits), a noticeable difference for outdoor readability. HDR peak: 600 vs 300 nits.
Key Differences
| Specification | ASUS ROG Strix XG309CM | LG UltraFine 40U990A-W |
|---|---|---|
| Refresh Rate | 220 Hz | 120 Hz |
| Response Time | 1 ms GTG | 5 ms GTG |
| Color Gamut | sRGB 110% | sRGB 100% · DCI-P3 99% |
| Screen Size | 29.5" | 39.7" |
| Resolution | 2560×1080 | 5120×2160 |
| Pixel Density (PPI) | 94 | 140 |
| Optimal Viewing Distance | 93cm | 62cm |
| SDR Brightness | 300 nits | 450 nits |
| HDR Peak Brightness | 300 nits | 600 nits |
| Contrast Ratio | 1:1,000 | 1:2,000 |
| Year | 2022 | 2025 |
All specifications
| Specification | ASUS ROG Strix XG309CM 2022 | LG UltraFine 40U990A-W 2025 |
|---|---|---|
| Screen Size | 29.5" | 39.7" (Better) |
| Resolution | 2560×1080 | 5120×2160 (Better) |
| Pixel Density (PPI) | 94 | 140 (Better) |
| Optimal Viewing Distance | 93cm | 62cm (Better) |
| Panel Type | IPS | IPS |
| Viewing Angle | 178° | 178° |
| Aspect Ratio | 21:9 | 21:9 |
| Refresh Rate | 220 Hz (Better) | 120 Hz |
| Variable Refresh Rate (VRR) | FreeSync Premium | FreeSync Premium |
| Response Time | 1 ms GTG (Better) | 5 ms GTG |
| HDR Certification | None | DisplayHDR 600 |
| SDR Brightness | 300 nits | 450 nits (Better) |
| HDR Peak Brightness | 300 nits | 600 nits (Better) |
| Contrast Ratio | 1:1,000 | 1:2,000 (Better) |
| Ports | 1x HDMI · 1x DP · USB-C · USB Hub | 2x HDMI · 1x DP · USB-C · USB Hub |
| USB-C Power Delivery | 15 W | — |
| Color Gamut | sRGB 110% (Better) | sRGB 100% · DCI-P3 99% |
| Year | 2022 | 2025 (Better) |
Frequently Asked Questions
Which has better PPI: ASUS ROG Strix XG309CM or LG UltraFine 40U990A-W?
The LG UltraFine 40U990A-W has 140 PPI compared to 94 PPI for the ASUS ROG Strix XG309CM.
Which has a closer optimal viewing distance?
The LG UltraFine 40U990A-W requires 62cm vs 93cm for the ASUS ROG Strix XG309CM to reach retina quality.
Related Comparisons
Alienware AW2725DF 27" 2024 · 110 PPI · 26.7" · 360 Hz
vs ASUS ROG Strix XG309CM 2022 · 94 PPI · 29.5" · 220 Hz
Alienware AW2725DF 27" 2024 · 110 PPI · 26.7" · 360 Hz
vs LG UltraFine 40U990A-W 2025 · 140 PPI · 39.7" · 120 Hz
Alienware AW3225QF 32" 2024 · 139 PPI · 31.6" · 240 Hz
vs ASUS ROG Strix XG309CM 2022 · 94 PPI · 29.5" · 220 Hz
Alienware AW3225QF 32" 2024 · 139 PPI · 31.6" · 240 Hz
vs LG UltraFine 40U990A-W 2025 · 140 PPI · 39.7" · 120 Hz
Methodology & Sources
Formula: Retina distance (cm) = 3438 / PPI. Displayed values are rounded for readability.
Sources: Official manufacturer spec sheets and product pages. Specs are normalized before comparisons.
Comparison winners are calculated metric by metric (higher is better for most specs; lower is better for distance/response time).
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