Hello again nautico,
Thank you for your question.
Methods for calculation seem to vary, but all seem to assume an 8.5 x
11" sheet size (if testing for a US printer and user). Resolution of
the image itself is not a factor, but "print quality" or the print
resolution is. See how a few testing labs calculate their ink costs,
perhaps a bit more accurately and "real world" than the manufacturer
might claim for the same printer:
ZDNET details their testing procedure as:
To determine an inkjet printer's cost per page, we install a new ink
cartridge in the printer and print special drain documents created in
Adobe Photoshop for the CMY (color) or K (black) cartridges. The K
drain document comprises 50 percent pure black bars and 50 percent
blank space. The CMY drain document is composed of alternating groups
of cyan, magenta, and yellow bars with blank spaces between the bars.
The printer outputs the documents until the image deteriorates due to
lack of ink or until the printer refuses to continue. This test yields
two cost-per-page numbers, one for the black ink cartridge and one for
the color ink cartridge.
Calculating cost per page
To determine the cost per page for black ink, we divide the current
street price of a replacement black cartridge by the number of pages
printed in the K drain. We then divide this result by 10 to determine
the cost per page based on an actual ink coverage average of 5
percent. Our labs uses a similar calculation for the CMY result. The
CMY cost-per-page calculation uses a 25 percent color-coverage figure
and assumes some black ink is also used in most color documents..."
"Ink Cost Test Procedures
We set the printer drivers to "Standard" or "Normal' settings which is
of course vendor dependent. We do not set any edge-to-edge printing
options but leave the printers at the defaults (some do not support
edge to edge printing). We have found that the actual printing area is
extremely close on all the printers tested if we use this method. We
use Adobe PhotoShop 6 to perform the tests.
BLACK (Nominal 5% coverage)
From PhotoShop we print copies of the file BlackTest.PSD repeatedly
until we detect a fault in the print quality of the output. The number
of full "perfect" pages are counted. We then take the first faulty
page and measure up to the point the ink started failing we then
calculate what proportion of a page this represents. For example we
might get 8.40 full pages before the ink starts to run out resulting
in a printing fault. We then use the following formula to calculate
the number of 5% coverage pages (discounting of course the outside
margin in this calculation).
Number of 5% black pages = (number of 100% pages) * (100/5)
In the above example the result is:
168 = 8.4 (100/5)
To then calculate the ink cost per page we use the following formula:
Ink cost per page = (Cost of black cartridge) / (Number of 5% black
COLOUR (no black and nominal 15% coverage)
Again we follow a similar procedure to the black test but this time
use the file "MASTER CMY.PSD" which was created in PhotoShop and
consists of 1/3 pure Cyan, 1/3 pure Magenta and 1/3 pure Yellow
arranged in three solid bands - we DO NOT tweak the colour to match
the printer. We count the number of full "perfect" pages and then
measure the point where the colour begins to first run out. For a
single tricolour cartridge this is as far as we go. But in the case of
clear individual C, M and Y cartridges we go a step further. We
measure the amount of ink in the cartridge when full then because
typically, but not always, only one of the three colours run out we
measure the remaining ink in the two partially empty cartridges.
For a Tricolour cartridge and individual ink tanks we then use the
Number of 15% pages = (number of 100% pages) * (100/15)
This will determine the number of pages from a tricolour cartridge
because effectively it is useless when one colour runs out. However we
need to go a step further for individual tanks to then enable us to
calculate a "truer" ink cost per page.
As an example VendorX's C, M and Y clear plastic ink tanks typically
contain 40mm of ink when full. After running the colour test until the
first ink tank just runs out we then measure the remaining ink in the
tanks. Lets say the results were:
Colour Used Remaining
Magenta 40 0
Yellow 37 3
Cyan 31 9
TOTALS 108 12
Say we obtained 60 colour pages at 100% coverage for VendorX's printer
up to the point where the Magenta just ran out.
So in effect 108mm of ink produced 60 pages.
Therefore the remaining 12mm of ink would produce the following number
Pages (100%) = 60 * (12 / 108)
Which of course equals 6.66 pages at 100%
We then calculate the 15% coverage as:
Colour pages (15% coverage) = 66.66 * (100 / 15)
The result of which is 444 pages. The total cost of all three CMY ink
tanks is then divided by 444 to yield the ink cost per 15% colour
page. If the CMY ink tanks were $20 each then the cost per page would
be determined as followed:
Ink cost per page = (total cost CMY tanks) / Number of 15% pages
Ink cost per page = ($20 + $20 + $20) / 444
Ink cost per page = 13.5 cents
COLOUR (with Black and nominal 20% coverage)
We simply calculate this page on 5% each of C, M, Y and K by adding
the cost calculated in the Black only scenario (black at 5%) to the
cost of the 15% colour (5% each C, M and Y but no black)."
You can see examples here, though your printer is not included in
their test list:
And PC Magazine notes their testing:
December 26, 2001
What Does It Really Cost?
By Jeremy A. Kaplan
"Figuring out the cost per page was the hard part of this formula. We
performed rundown tests on each printer to determine how many pages of
our test target each unit could actually print before its cartridges
ran out of ink. Half the target contains black text; the other half
contains cyan, magenta, yellow, and black color blocks that represent
color output (keep in mind that black is an important part of any
Printer companies traditionally cite cost-per-page numbers based on a
document with 5 percent black text coverage - essentially a typed,
double-spaced page. Color pages are based on 15 percent coverage.
These are pretty unrealistic documents, however, so we took to the Web
to come up with more realistic information.
First we ran a survey on PCMag.com to ascertain whether people print
more text-only files or graphics files. According to these results,
people print approximately half text files and half graphics files
(including photos), as well as a number of Web site pages. Next, we
downloaded and analyzed many common Web sites to determine what
percentage of Web pages are covered by ink once they're printed. It
turns out that 8 percent of an average printed Web page is text and 8
percent is graphics or photos. So our target is covered in 8 percent
black ink and 8 percent color16 percent total.
Determining the cost per page (we cite the cost per average page,
rather than the cost of a black page or a color page) is the
challenging part. We started with the cost of a regular-capacity black
cartridge, rather than the high-capacity or starter cartridges
sometimes supplied; divided it by the number of pages printed before
the black ink ran out; and multiplied this figure by 62.5 percent. The
62.5 percent figure is important because of the nature of our test
target. Half the target is text, and half is color; remember that
black makes up one-quarter of the color half as well. One quarter of
one half (or 12.5 percent) plus the 50 percent for the all-text half
yields a total of 62.5 percent coverage. We determined color ink costs
similarly: the cost of the cartridge divided by the number of pages
output times 37.5 percent. Black ink cost per page plus color ink cost
per page equals the average cost per page..."
It would seem that their calculations are more real world and more
informative for the average user.
Most of the online cost per page calculators are very rudimentary and
seem to target just estimating printing costs for companies or
departments for budgetary concerns. For example:
Document Cost Calculator
Use this interactive calculator to determine your document production
Here they assume .08 -.30 per page for inkjets, which doesn't really
address your question.
There are few software programs to calculate costs. The following is
primarily for laser printers, but would seem to work inkjets as well:
Image Analyser Software with Cost Per Page Calculator
PageCheck automatically scans your documents, measures the page
coverage (of a single page or average of 6 pages) and calculates the
true cost per page you are likely to obtain.
PageCheck compares the manufacturer's claims and cost-per-cartridge
against you actual scanned documents to show you the real cost per
SCANS: You simply install PageCheck onto a computer that has a
standard TWAIN scanner. At the press of a button, PageCheck fires up
your scanner and allows you to import and save the document image.
PageCheck uses the latest 8 bit imagery and handles mono or color
...PageCheck contains a built in calculator designed to work out your
cost per page. You simply key in the price per cartridge, the
manufacturers estimate page yield, the % coverage that the
manufacturer used and the actual coverage of your own document
(measured in PageCheck as a single page or average of multiple pages).
I was unable to locate any similar programs. And, unfortunately, this
program seems very pricey at a single user license of $899 yearly:
Finally, I checked to see what others claimed as the cost per page for
your "OfficeJet G55":
Color HP45 Black 42ml
Page yield: 833 (based on 5% coverage)
Color HP78 Tri-color (AN=38 ml, DN=19 ml)
Yields: 970 pages (C6578AN); based on 15% coverage
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I trust my research will be helpful for you to determine your actual
costs per page on this printer.
If a link above should fail to work or anything require further
explanation or research, please do post a Request for Clarification
prior to rating the answer and closing the question and I will be
pleased to assist further.