Canon PG-645 Ink Replacement Guide: Match Black, Colour and XL Cartridges
Replacing printer ink is a part-number task before it is a colour or price decision. A name such as “Canon 645” can appear on more than one cartridge, and a black cartridge is not a substitute for a colour cartridge simply because the number looks similar. The safest approach is to identify the code shown by your printer or its current cartridge, then match that exact code, colour and any XL marking to the listing.
Read the cartridge code as three separate clues
For the products in this guide, the most useful clues are the number, the colour and the XL label. The live KW Tech title for SKU PG645OCN identifies it as Canon PG645 FINE Black Ink Cartridge STD. The live title for SKU 2485225 identifies a PG645XL FINE Black cartridge, while SKU CL646XLOCN is identified as Canon CL646XL Colour High Yield Ink Cartridge.
Those labels describe distinct products. Treat them as a checklist rather than as interchangeable shorthand: first match the code family; then confirm whether you need black or colour; finally check whether the replacement is marked XL. If the code on the printer, packaging or manufacturer support material does not match, pause and verify it before opening a cartridge.
Choose black or colour based on the cartridge you are replacing
A practical starting point is to look at the empty cartridge, not at the colour of the document you plan to print. The product names here make the distinction clear: the PG645 listings are black, and the CL646XL listing is colour. If your printer reports a particular cartridge is low or empty, match that reported code and colour exactly.
Keeping the codes in a note near the printer is useful in a home office, classroom or small workplace. It saves a last-minute purchase from becoming a guess, especially when more than one Canon printer is in use. The linked product page and SKU are a better reference than a generic search for “Canon ink”, because the listing gives a specific item to compare against your existing cartridge.
What the XL marking changes in your shortlist
XL is part of the product identification, not a detail to omit. The two XL products below have XL in their names: PG645XL Black and CL646XL Colour. The other black product is listed as PG645 STD. Choose the exact code your printer documentation calls for, then decide between the specific standard or XL option that applies to that code.
Do not rely on a similar-looking box, a nearby product number or an assumption that XL means every product in a family will fit the same printer. When you need information beyond the live listing—such as printer compatibility or page yield—check the exact Canon documentation for your printer model and cartridge code. That is especially important before stocking supplies for several devices.
A five-step ink replacement check
- Read the alert or old cartridge. Record the full printed code, including letters and XL.
- Confirm the colour. Match black with black, or colour with colour, as identified on the cartridge.
- Compare the full listing title. Check the code, colour and standard/XL wording against the item you recorded.
- Keep the SKU with the code. A SKU such as PG645OCN or CL646XLOCN makes it easier to find the same exact listing later.
- Verify before opening. If any part number differs, check the printer manual or Canon’s exact product information first.
Verified Canon ink cartridges to compare
These cards use current KW Tech Shopify data. Prices and availability can change, so use the linked product page as the current reference before deciding.
Make the replacement a match, not a guess
The right cartridge begins with the exact code already associated with your printer. Use PG645 versus PG645XL, black versus colour, and the product SKU as separate checks. With those details matched before you order, you have a clear, repeatable way to buy the correct item without turning a routine ink replacement into an avoidable compatibility problem.