Your Epson ColorWorks (C3500, C4000, C6000, or C7500) is throwing a "Media Size Error" and won't print. The ink is fine, the labels are loaded, the media type is set correctly — but the printer stubbornly refuses. The problem? Your label dimensions are off by more than 1mm.
Epson ColorWorks printers are precise machines with 1mm tolerance on media dimensions. If you enter 103mm when your label is actually 100mm, the printer detects the mismatch and throws the error. Unlike thermal printers that are more forgiving, ColorWorks firmware strictly validates dimensions against what the sensor physically measures.
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Why This Error Happens
When you set up a media definition template in the Epson driver, you enter width and height values. The printer then compares these values against what it physically detects:
- For die-cut labels: the sensor measures the gap-to-gap distance (height) and the media width
- For black mark labels: the sensor measures mark-to-mark distance
- For continuous labels: only width is validated (height is whatever you print)
If your entered dimensions don't match what the sensor measures — with more than 1mm difference — the printer throws Media Size Error and stops.
The Width vs Height Rule (This Is Where Everyone Gets Confused)
The single biggest cause of Media Size Error is swapping width and height. Epson defines these differently than you might expect:
Width = the dimension parallel to the printer mouth (the edge of the label that runs across the print head, left to right).
Height = the dimension perpendicular to the printer mouth (the edge of the label in the feed direction, front to back — the direction the paper moves).
Think of it this way: if you're standing in front of the printer looking at the label slot:
| Dimension | Direction | How to Identify |
|---|---|---|
| Width | ← Left to Right → | Runs across the printer mouth, parallel to the print head |
| Height | ↑ Feed direction ↓ | Runs in the direction the paper feeds through the printer (at 90° to the mouth) |
Look at your label as it exits the printer. The edge coming out first is the height direction. The edge running side to side across the exit slot is the width direction.
Continuous Labels: Height Doesn't Matter
If you're using continuous labels (no gaps, no marks), only the width needs to be accurate. The height value tells the printer how long each "page" should be — since there are no physical label boundaries, the printer can't detect height mismatches. Width, however, is still validated by the sensor and must be within 1mm.
How to Measure Correctly
Measure only the label itself — not the backing paper, not the gap, not the total roll width. Just the printed/printable area of a single label.
Use calipers if you have them — a ruler works but calipers give you sub-millimeter accuracy. For Epson ColorWorks, you need to be within 1mm.
Measure the width: hold the label as it would sit in the printer. The edge that runs parallel to the printer mouth (left-right) is the width.
Measure the height: this is the edge in the feed direction (the 90-degree dimension relative to width).
Don't round generously. If your label measures 49.5mm, enter 49.5mm or 50mm — not 52mm. Every millimeter counts.
Common Mistakes That Trigger the Error
| Actual Label | What You Entered | Result | Why |
|---|---|---|---|
| 100mm × 50mm | 50mm × 100mm | ❌ Error | Width and height are swapped |
| 100mm × 50mm | 100mm × 53mm | ❌ Error | Height is off by 3mm (exceeds 1mm tolerance) |
| 100mm × 50mm | 100mm × 50.5mm | ✓ Works | Within 1mm tolerance |
| 100mm × 50mm | 100.8mm × 50mm | ✓ Works | Within 1mm tolerance |
| 76mm × 51mm | 76mm × 54mm | ❌ Error | Height is off by 3mm |
Setting Correct Dimensions on C3500
Go to Windows Settings → Printers & Scanners → Epson C3500 → Printing Preferences
Open the "Media Definition" tab
Select your media template (or create a new one)
In the Width field, enter the measurement parallel to the printer mouth
In the Height field, enter the measurement in the feed direction
Save the template and send a test print
Setting Correct Dimensions on C7500
Same concept, slightly different driver UI:
Open Printing Preferences for your Epson C7500
Go to "Media" or "Media Definition"
Enter width and height carefully — the C7500 uses the same parallel/perpendicular convention
If you also see a "Gap" field (for die-cut), enter the gap size between labels accurately
Save and test print
If dimensions are correct but you still get Media Size Error, the issue might be media type mismatch instead — your sensor mode (die-cut vs continuous vs black mark) doesn't match your label. See our Media Form Error fix guide for that.
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LabelInn sends your label dimensions directly to the Epson ColorWorks, bypassing the Windows driver entirely. No templates to create, no width/height confusion, no 1mm guessing game. Works on Windows, macOS, iOS, and Android.
Try LabelInn Free for 14 Days →Frequently Asked Questions
How precise do my label measurements need to be for Epson ColorWorks?
Within 1mm. If your actual label is 100mm wide and you enter 102mm in the driver, the printer will throw a Media Size Error. Use calipers for best accuracy, or at least a good ruler.
Why does swapping width and height cause an error?
Because the printer measures the physical media against your entered values. If you enter 100mm width but the printer measures 50mm across the print head, that's a 50mm difference — far beyond the 1mm tolerance.
What about the gap size — does that factor into height?
No. Enter the label height only — not label + gap. The gap size is a separate field in the media definition. The printer uses the gap value to know how far to skip between labels, but it's not added to the height.
Do I need to enter height for continuous labels?
You need to enter a height value (it determines the length of each printed "page"), but the printer won't throw a Media Size Error for height on continuous labels since there are no physical boundaries to validate against. Width must still be accurate.