I have an HP all-in-one color printer/scanner/copier (OfficeJet G55)
on which I print both color and B&W photos. The rate of ink drainage
from the color cartridge can be extraordinary, depending, of course,
on several factors. When I asked HP for cost-per-print info, I recd
the following response:

Dear Bob,

It is very difficult to determine the exact cost for printing one
page.
There are various factors that determine the cost of a page printed
out.
Some of them are whether the printout taken is a color or a black and
white printout, the size of printout taken etc.  However I would 
recommend that you refer the following Web site for information on the
cost per page based on approximates:

http://h20015.www2.hp.com/en/document.jhtml?lc=en&docName=bpu03033

It is important to us that we answer your question.  If you need 
further assistance, please reply to this message, we will be happy to
help you.


Sincerely,
Robin
HP Consumer e-Support

The web page that HP cites above is too simplistic to be helpful. It
would seem that a calculator could be devised that would take into
account the following parameters:

a) Cartridge type
b) Cartridge cost
c) Color or B&W
d) Resolution of scan
e) Paper size
f) Paper type (i.e., whether printer is set at "best," "normal," or
"fast")

Does such a calculator currently exist?

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:
http://www.zdnet.com/products/stories/reviews/0,4161,2862742,00.html

"Printer-economy tests

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..."

RMIT:
http://www.testlab.rmit.edu.au/inkjet_test_procedures.php

"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
pages)


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
following formula:

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
of pages:

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:
http://www.testlab.rmit.edu.au/graphs.php

And PC Magazine notes their testing:
http://www.pcmag.com/article2/0,4149,3195,00.asp

Ink Again
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
color image).

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 color—16 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:

http://www.equitrac.com/calculator/default.htm
Document Cost Calculator

Use this interactive calculator to determine your document production
costs.

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:

http://www.bertl.com/pagcheck.html
PageCheck 

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
page.
  
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
documents...

...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:
http://www.digital-times.net/scripts/purchase/index.cfm

Finally, I checked to see what others claimed as the cost per page for
your "OfficeJet G55":

VarGlobal
http://www.varglobal.com/Cartridges.htm

51645A  US$$30.00 
Color HP45 Black 42ml 
Page yield: 833 (based on 5% coverage)

C6578AN  US$55.00/piece
Color HP78 Tri-color  (AN=38 ml, DN=19 ml) 
Yields: 970 pages (C6578AN); based on 15% coverage


Search Strategy:

inkjet +"cost per page"
inkjet +"cost per page" +calculator
"cost per page" +calculator
"cost per page" +software OR program
inkjet +"cost per page" +software OR program
inkjet +"cost per page" +test OR monitor
"cost per page calculator" 
calculate +"cost per page" 
"OfficeJet G55" +"cost per page" 

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.

Regards,

-=clouseau=-

---

Request for Answer Clarification by nautico-ga on 25 Apr 2003 11:49 PDT

What you found is what I expected, namely, that there's no simple way
for the home user to forecast cartridge drain rate and the resultant
per-page cost based on the kinds and sizes of photos estimated to be
printed over the life of the cartridge. Studies cited have focused
more on costs of printing web pages or bulk business printing costs,
not on individual photo printing costs typical of home users. In any
event, I thank you for the exhaustive research. Case closed.

---

Clarification of Answer by clouseau-ga on 25 Apr 2003 12:11 PDT

Thank you once again for the rating and tip.

I'm sorry I could not locate a program you were hoping to find, but as
you say, these seem to be tailored to the needs of the corporate user
rather than a home user's needs.

I will keep an eye out as this question has obviously piqued my
interest. If I find anything additional, I will be sure to post here
in this question.

Best regards,

-=clouseau=-

---

Request for Answer Clarification by nautico-ga on 25 Apr 2003 13:45 PDT

I think I'd disagree that "resolution is not a factor" in influencing
cartridge drain, as I've noticed a difference when printing low res
vs. high res photos in terms of a detectable change in the printer
software's ink usage meter. I would guess that I would use up an
entire color cartridge if I were to print, say, 15 color 8x10 photos
at a 1600x1200 res, though I don't intend to conduct that experiment
for the $50 it would cost.

---

Clarification of Answer by clouseau-ga on 25 Apr 2003 14:18 PDT

I'm surprised.

I can easily understand a difference from the "print quality" setting
which changes the resolution and the amount of dots or droplets the
printer will print. But the resolution of the original image should
not effect the amount of ink as the printed image size remains the
same as does the amount of droplets used by the printer at any given
setting of the printer.

I'm trying to think this through more completely - thinking out loud
here - , and I imagine if there were a gross difference in the image
resolution, say 100 dpi to 600 dpi, it might cause the printer to
print more droplets for the same image size up to the minimum size
limit of the droplet for the printer, so, perhaps you are correct.

I did a quick search for "ink usage" +"image resolution" and did not
find much, however the discussions on this page are interesting:
http://www.ekdahl.org/printerinfo.htm

And this page linked from the above would seem to validate your
thought that more ink is required for higher image resolution at the
sam eprinter setting:
http://www.imaging-resource.com/TIPS/PRINT1/PRINT1A.HTM

Pixels, Dots, and Inches: How Big Can I Print It
By Dave Etchells

Note the images at the bottom of the page. So, indeed. more packed
pixels in the original image create the need for more droplets from
the printer at the same printer resolution.

Apologies for not thinking this through more in my original answer.

-=clouseau=-

---

Request for Answer Clarification by nautico-ga on 25 Apr 2003 14:38 PDT

I appreciate your continuing to pursue this after we've closed the
case. I think we can now agree that increased resolution/pixel density
equals increased ink drain, though I'm not sure the relationship is
perfectly linear. Cartridge makers/sellers like HP are clearly not
interested in providing users with precise tools for measuring per pic
printing costs. I've concluded that for high res 8x10 prints it makes
a lot more sense to transmit the .jpg file to sites like Kodak's Ofoto
than to print it out on one's own machine.

---

Clarification of Answer by clouseau-ga on 25 Apr 2003 14:55 PDT

My pleasure. I'm never happy until my customers are satisified with
their answer.

Ofoto has received very high ratings for image printing and value at
many of the digital sites. If you are not already familiar with this
one, it is probably the best of the best when it comes to information
on almost anything relating to digital photography. Do check out their
user forums as well as articles, links and reviews.

http://www.steves-digicams.com/

Best,

-=clouseau=-

---

Request for Answer Clarification by nautico-ga on 25 Apr 2003 18:01 PDT

Interesting you mentioned Steve's Digicams site, as it was based on
his review that I bought my digital camera.

---

Clarification of Answer by clouseau-ga on 25 Apr 2003 18:12 PDT

Steve's is excellent info.

I need to let you know that Requests for Clarification trigger a
notice to the researcher and place a large memo on our researcher page
that we need to reply to a clarification. In order to clear that, we
must post a Clarification.

If a comment is posted, we are not notified, but you are. However,
checking our recent answers on a researcher page will show the recent
comment activity and we can check to see if a reply is called for and
needed.

This isn't a problem, and not something you would know from the GA
terms, FAQ's , etc. But just so you do know, I'm going to have to have
the last word sometime! 8^)

Best,

-=clouseau=-

Exhaustive and informative research, though not the answer I'd hoped
for. There simply isn't a simple calculator available that would
enable the typical home user to calculate photo printing costs based
on cartridge drainage rates.