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Open-File Report 2010–1280

Florida Shelf Ecosystems Response to Climate Change Project

CO2calc: A User-Friendly Seawater Carbon Calculator for Windows, Mac OS X, and iOS (iPhone)

By L.L. Robbins, M.E. Hansen, J.A. Kleypas, and S.C. Meylan

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A user-friendly, stand-alone application for the calculation of carbonate system parameters was developed by the U.S. Geological Survey Florida Shelf Ecosystems Response to Climate Change Project in response to its Ocean Acidification Task. The application, by Mark Hansen and Lisa Robbins, USGS St. Petersburg, FL, Joanie Kleypas, NCAR, Boulder, CO, and Stephan Meylan, Jacobs Technology, St. Petersburg, FL, is intended as a follow-on to CO2SYS, originally developed by Lewis and Wallace (1998) and later modified for Microsoft Excel® by Denis Pierrot (Pierrot and others, 2006). Besides eliminating the need for using Microsoft Excel on the host system, CO2calc offers several improvements on CO2SYS, including:

  • An improved graphical user interface for data entry and results
  • Additional calculations of air-sea CO2 fluxes (for surface water calculations)
  • The ability to tag data with sample name, comments, date, time, and latitude/longitude
  • The ability to use the system time and date and latitude/ longitude (automatic retrieval of latitude and longitude available on iPhone® 3, 3GS, 4, and, in the future, Windows® hosts with an attached National Marine Electronics Association (NMEA)-enabled GPS)
  • New constants, including Lueker and others (2000) and Millero (2010)
  • The ability to process multiple files in a batch processing mode
  • An option to save sample information, data input, and calculated results as a comma-separated value (CSV) file for use with Microsoft Excel, ArcGIS,® or other applications
  • An option to export points with geographic coordinates as a KMZ file for viewing and editing in Google EarthTM

First posted December 13, 2010


  • PC or Macintosh Files version 4.0.9
  • PC or Macintosh Files version 1.3.0

    Use a browser other than Chrome or Edge to open the executable files.

    This software will operate on both PC and Mac, if Silverlight is installed on your computer. In order for CO2calc software to operate correctly, it must be installed directly onto your computer. Although it will not run on the internet, you will be notified if updates in the software are available.

    The latest version of the Silverlight software can now be downloaded.

  • iPhone: iTunes link or type "co2calc" in the App Store's search bar
    (Requires iOS 4.2 or later.)

For additional information contact:
Lisa Robbins
U.S. Geological Survey
St. Petersburg Coastal and Marine Science Center
600 4th Street South
St. Petersburg, FL 33701

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Robbins, L.L., Hansen, M.E., Kleypas, J.A., and Meylan, S.C., 2010, CO2calc—A user-friendly seawater carbon calculator for Windows, Max OS X, and iOS (iPhone): U.S. Geological Survey Open-File Report 2010–1280, 17 p.




Additional Features

Additional Constant from Lueker and Others (2000)

Millero (2010) Constants for Estuarine Waters

Air-Sea CO2 Flux

Running CO2calc on Windows or Mac OS X

Entering Sample Information

Entering Input Data

Viewing and Exporting Output Data

Recording Calculations

Batch Processing

CSV to KML/KMZ Translation

Running CO2calc on iOS (iPhoneOS)

Entering Sample Information

Entering Input Data

Viewing Output Data

Deleting and Emailing Stored Calculations


References Cited

Appendix A. Constants

Appendix B. About pH

Appendix C. fCO2, pCO2

Appendix D. KSO4

Appendix E. Options

Appendix F. Pressure Effects

Appendix G. Calcium Carbonate Solubility (Ω), Alkalinity, and the Revelle Factor

Appendix H. Air-Sea CO2 Flux and Conversions

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