You've just installed a fresh cartridge and already your printer is warning you the ink is low. Or you're mid-print job and the warning appears, but the output looks perfectly fine. It's one of the more baffling things printers do — and it happens to a lot of people. Here's what's actually going on.
Ink Levels Are Estimated, Not Measured
This surprises most people: the vast majority of inkjet printers don't directly measure how much ink is left in a cartridge. Instead, they use software algorithms to estimate ink levels based on how many pages have been printed and how much ink each page is calculated to have used.
These estimates are deliberately conservative. Printer manufacturers programme low ink warnings to trigger with a meaningful buffer remaining — partly to protect the print head from running completely dry (which can cause damage), and partly to give you time to order a replacement before you run out mid-print. The result is that a low ink warning often means "getting lower" rather than "nearly empty", and there can be a surprising amount of usable ink still available.
In short: if your prints still look good, you can generally keep printing regardless of what the warning says.
Cartridge Chips Don't Always Get It Right
Most modern ink cartridges contain an embedded chip that communicates with the printer — tracking usage, reporting ink status, and in some cases preventing printing below a certain threshold to protect the print head. These chips serve a genuine purpose, but they're not infallible.
The chip tracks ink consumption rather than directly sensing the ink level, so if printing patterns vary — lots of coverage on some pages, very little on others — the chip's estimate can drift from reality. Cartridges that have been removed and reinstalled can also confuse the sensor, as the chip may register the reinstallation as a new usage event. And chips on non-genuine or refilled cartridges are more prone to misreporting, since they weren't calibrated for the ink formulation they're now being used with.
Ink Can Settle or Shift Inside the Cartridge
Ink cartridges aren't just simple tanks of liquid — they contain internal sponges and channels that distribute ink towards the nozzles. If a cartridge has been sitting unused for a period, or if the printer has been stored in a particular orientation, ink can settle or become trapped in parts of the cartridge that the sensor reads as empty.
In some cases, very gently shaking or rotating the cartridge can help redistribute the ink and temporarily resolve a premature low ink warning. This isn't a permanent fix, but it can squeeze additional pages out of a cartridge that's reading as lower than it actually is. Be cautious — don't shake vigorously or you risk damaging the cartridge or causing leaks.
What to Actually Do About It
The most practical approach is to treat a low ink warning as a prompt to order a replacement, not as a signal to stop printing immediately. Continue printing as long as the output quality remains good. When colours start to look faded, streaky, or patchy, that's the more reliable indicator that the cartridge is genuinely running low.
A few other things worth knowing:
Using genuine cartridges from HP, Canon, Epson, or Brother gives you the most accurate ink level reporting, since the chip is calibrated for the exact ink formulation in the cartridge. Compatible or refilled cartridges are more likely to produce unreliable readings.
Checking for printer firmware updates occasionally is also worthwhile. Manufacturers sometimes issue updates that improve ink level accuracy or adjust the threshold at which warnings are triggered.
Avoid removing and reinstalling the same cartridge repeatedly when troubleshooting a warning — each reinstallation can reset or confuse the chip's tracking and may make the readings less reliable rather than more.
When the Cartridge Really Is Empty
When you do finally need to replace a cartridge, don't bin the empty one. At Crazy Kangaroo, every HP and Canon ink order includes a free prepaid recycling bag — just pop your empties in and drop it in the post. You can also download a free Freepost recycling label at any time for any brand, and recycle from home at no cost.
