The pixel pitch of a typical 3.2 inch 240x320 TFT display is approximately 0.2025 millimeters (mm) per pixel. This number comes from dividing the display’s active area width by the horizontal resolution. For a standard 3.2 inch diagonal screen with a 3:4 aspect ratio, the active area is roughly 48.6 mm wide by 64.8 mm tall. So, 48.6 mm divided by 240 pixels gives you 0.2025 mm per pixel horizontally, and 64.8 mm divided by 320 pixels gives you the same 0.2025 mm vertically. That means every square pixel on this screen measures about 0.2025 mm on each side. This is a critical spec for anyone designing embedded systems, handheld devices, or industrial interfaces, because it directly affects how sharp text and icons look up close.
Now, let’s break down why this pixel pitch matters. Pixel pitch, sometimes called dot pitch, is the distance from the center of one pixel to the center of the next. A smaller pixel pitch means higher pixel density, which translates to sharper images. For a 3.2 inch 240x320 TFT, the pixel density is around 125 pixels per inch (PPI). That’s a moderate PPI—not as sharp as a modern smartphone (which can hit 400+ PPI), but perfectly adequate for basic GUIs, menu systems, or data readouts. The trade-off is that larger pixel pitches make individual pixels more visible, especially when you’re viewing the screen from a few inches away. At 0.2025 mm, you’ll barely see the grid if you’re holding the device at arm’s length, but if you press your nose against it, you’ll notice some jaggedness on curved lines.
Digging into the hardware, a 3.2 inch 240x320 tft display module typically uses a TFT (Thin-Film Transistor) LCD panel with an active matrix structure. Each pixel contains three sub-pixels—red, green, and blue—arranged in a vertical stripe pattern. The pixel pitch of 0.2025 mm applies to the entire pixel, not the sub-pixels. Sub-pixel pitch is roughly one-third of that, around 0.0675 mm, but that’s not a standard spec you’ll see in datasheets. The active area itself is usually 48.6 mm x 64.8 mm, with a tolerance of ±0.2 mm depending on the manufacturer. The glass thickness is typically 0.55 mm to 0.7 mm, and the overall module thickness, including the backlight and FPC (Flexible Printed Circuit), can be 2.5 mm to 3.0 mm. These physical dimensions are important for enclosure design and optical bonding.
Let’s talk about the relationship between pixel pitch and viewing distance. The human eye can resolve details down to about 1 arcminute (0.0167 degrees) under ideal conditions. For a pixel pitch of 0.2025 mm, the minimum viewing distance where you can’t distinguish individual pixels is about 0.2025 mm / tan(0.0167°) ≈ 0.2025 mm / 0.000291 ≈ 696 mm, or roughly 27.4 inches. That means if you’re using this display in a handheld device held at 12 to 18 inches, you’ll likely see some pixel structure. But for industrial panels mounted at arm’s length (around 24 inches), it’s acceptable. Compare that to a 0.1 mm pixel pitch display (like a 5 inch 1080p panel), which would be sharp at 14 inches. So, the 0.2025 mm pitch is a compromise between cost, power consumption, and readability.
From a manufacturing perspective, the pixel pitch is determined by the lithography and etching processes used to create the TFT array. The 240x320 resolution at 3.2 inches is a standard QVGA (Quarter Video Graphics Array) format, which has been around since the early 2000s. The glass substrate is usually a Gen 2 or Gen 3 size, cut into individual panels. The pixel pitch of 0.2025 mm corresponds to a resolution of about 125 PPI, which is typical for displays in this size range. For comparison, a 2.8 inch 240x320 display has a smaller active area (about 43.2 mm x 57.6 mm), giving a pixel pitch of 0.180 mm and a higher PPI of 141. So, the same resolution in a smaller screen yields a finer pitch. Conversely, a 3.5 inch 240x320 display has a larger active area (about 53.2 mm x 70.9 mm), with a pixel pitch of 0.222 mm and a lower PPI of 114. The 3.2 inch version sits right in the middle.
Here’s a quick table to show how pixel pitch varies across common display sizes with the same 240x320 resolution:
| Diagonal Size (inches) | Active Area Width (mm) | Active Area Height (mm) | Pixel Pitch (mm) | PPI |
|---|---|---|---|---|
| 2.8 | 43.2 | 57.6 | 0.180 | 141 |
| 3.2 | 48.6 | 64.8 | 0.2025 | 125 |
| 3.5 | 53.2 | 70.9 | 0.222 | 114 |
This data is based on standard mechanical drawings from major TFT manufacturers like BOE, AUO, and Tianma. The 3.2 inch module typically uses an ILI9341 or ST7789 driver IC, which supports 16-bit or 18-bit color depth. The pixel pitch directly influences the aperture ratio—the percentage of each pixel area that actually transmits light. For a 0.2025 mm pitch with a 3 µm (0.003 mm) black matrix gap between pixels, the aperture ratio is roughly (0.2025 - 0.003)^2 / 0.2025^2 ≈ 97%. That’s high, which means good brightness efficiency. The backlight is usually a 4-LED white array with a brightness of 300 to 500 cd/m², so the effective luminance per pixel is decent.
Now, let’s get into the nitty-gritty of how pixel pitch affects interface design. If you’re coding a GUI for this display, you need to account for the fact that a 1-pixel-wide line will be 0.2025 mm thick. For a touch interface, the recommended minimum touch target size is 7 to 10 mm, which translates to about 35 to 49 pixels. So, buttons should be at least 40x40 pixels to be comfortable for finger use. Text readability also depends on pixel pitch. At 125 PPI, a 10-point font (about 3.5 mm tall) will be roughly 17 pixels high, which is readable for most users. But if you use a 6-point font (2.1 mm), it’s only 10 pixels high, and the character details will be blurry. The pixel pitch also limits anti-aliasing effectiveness—sub-pixel rendering, like ClearType, works best at pitches below 0.15 mm, so on this display, you’ll see some color fringing on text.
From a reliability standpoint, the pixel pitch is tied to the TFT’s line width and spacing. The gate and data lines are typically 3 to 5 µm wide, with a 5 to 10 µm spacing. A 0.2025 mm pixel pitch means the horizontal pitch is 202.5 µm, which leaves plenty of room for these lines. The parasitic capacitance between lines is low, so the display can achieve a refresh rate of 60 Hz without ghosting. However, if you’re driving the display at higher frame rates (like 120 Hz for animation), the pixel pitch might cause slight crosstalk due to RC delays in the row and column drivers. The typical response time for a 3.2 inch TFT is 20 to 30 ms (gray-to-gray), which is fine for static images but can show motion blur for fast-moving objects.
Let’s compare this pixel pitch to other common display technologies. An OLED panel of the same size and resolution would have a pixel pitch of about 0.2025 mm as well, but the sub-pixel arrangement is different—OLEDs often use a PenTile or Diamond layout, which can make the effective pixel pitch appear larger. For LCDs, the pixel pitch is uniform across the entire active area, with a tolerance of ±0.005 mm. The viewing angle also interacts with pixel pitch. With a wide viewing angle (typically 80° left/right, 80° up/down for IPS panels), the pixel pitch becomes less noticeable off-axis because the light spreads. But for TN panels (narrower viewing angles), the pixel pitch can cause color shift at the edges because the liquid crystal alignment varies.
In terms of cost, a 0.2025 mm pixel pitch is cheap to manufacture. The mask sets for 240x320 resolution are mature, and the yield rate is high (above 95% for most fabs). The unit price for a 3.2 inch TFT module in volume (1000+ pieces) is around $5 to $8, depending on the interface (SPI, parallel, or RGB). The pixel pitch doesn’t directly affect the BOM cost, but it does influence the backlight design. A smaller pitch would require a brighter backlight to maintain the same perceived brightness, because the black matrix takes up more area. At 0.2025 mm, the backlight power is typically 150 to 200 mW, which is fine for battery-powered devices.
One practical consideration: if you’re using this display in a product that requires high legibility under direct sunlight, the pixel pitch of 0.2025 mm means the contrast ratio (typically 500:1 to 1000:1) will be the limiting factor, not the pitch itself. The reflectance of the TFT surface (about 4% without AR coating) can cause glare, but the pixel pitch doesn’t contribute to that. For outdoor use, you might want a transflective or high-brightness version, but those often have the same pixel pitch. The 0.2025 mm pitch is also compatible with standard capacitive touch panels, which have a sensor pitch of 4 to 5 mm, so there’s no interference.
Finally, let’s look at how the pixel pitch affects the display’s electrical interface. The ILI9341 driver IC, commonly used with this module, has a RAM size of 240x320x18 bits, which is about 1.38 Mbits. The pixel clock for SPI mode is typically 10 to 20 MHz, so the time to update one pixel is 0.05 to 0.1 µs. That means a full screen refresh takes about 3.8 to 7.7 ms, ignoring overhead. The pixel pitch doesn’t change the electrical timing, but it does affect the gamma correction curves. The driver IC has a programmable gamma table that adjusts the voltage for each gray level, and the pixel pitch influences the perceived brightness uniformity. For a 0.2025 mm pitch, the gamma curve is usually set to a standard 2.2, but you can tweak it for better contrast in dark scenes.