One is a way to calculate the amount of climate-warming gases released through a company’s supply chain, as well as in the use and disposal of its products. A standardized way of calculating such emissions had eluded energy experts and statisticians for several years. The tool is known as Scope 3.

The second tool is for calculating the emissions of carbon dioxide, methane and four other gases linked to climate change across a consumer product’s entire life cycle. With a toaster, for example, a company would seek to count greenhouse gases released in the mining of elements for its metal shell and the coal burned to make the electricity to power it — and even the fuel burned when the toaster is carted away.

Now that there is a method for tallying those emissions, experts hope to refine it in years to come, perhaps eventually enabling consumers to compare the greenhouse gas footprints of, say, two frozen dinners or two sofas.

In 2004 the World Resources Institute, a Washington-based environmental organization, and the World Business Council for Sustainable Development released a final standard for Scope 1 and Scope 2. Scope 1 covers emissions from direct operations like running a factory. Scope 2 covers emissions from energy-related, indirect sources of emissions like the coal or natural gas burned to make the electricity that powers the lights at headquarters.

Scope 3 measures the emissions linked to the “value chain” of a company’s products as a whole. The life cycle emissions of individual products, including Scope 3 emissions, can be estimated using the second tool.

The 2004 corporate standard has taken hold as the dominant accounting methodology for greenhouse gases. The Carbon Disclosure Project, a nonprofit group that uses investor leverage to pressure corporations to disclosure their emissions, says that most of the corporations that report to the project use the GHG protocol template.

While the standards are voluntary, Pankaj Bhatia, director of the GHG Protocol, the joint venture of the two nonprofits that produced the standards, predicted that companies would adopt them because it helped them hone their business strategies. “Armed with these new standards, companies can see the full picture of their emissions,” he said.

Advocates of the standards suggest that the mere act of measuring greenhouse gas emissions — and having a meaningful way of comparing that output with that of competitors — has encouraged companies to manage and reduce what they emit.

Even with the new tools, however, it will not be an easy task for companies to measure Scope 3 emissions with much specificity. Many smaller subcontractors in developing nations that manufacture or provide components to larger entities have no useful way of measuring their energy use.

In such cases, the protocol has allowed for the use of local industry-specific energy use averages.

In developing the new standards, the institute and the business council worked with more than 60 corporations to test the standards and solicit feedback. Dan Pettit, associate director of sustainability for Kraft Foods, said that his company learned while working with the new protocols that Scope 3 emissions — coming from activities like farming — accounted for 90 percent of the overall impact.

The company is now trying to work with a few high-emission areas for reductions, such as helping cocoa producers in Ghana increase crop yields while minimizing use of carbon-intensive fertilizer, he said.

Kraft has a financial incentive to make progress on that front, Mr. Pettit said. “Think of carbon as waste — somewhere there is inefficiency.”

Linda Fisher, the chief sustainability officer for the chemical company DuPont, said that a product’s estimated carbon footprint could be a useful sales tool.

DuPont’s businesses have “very much seen their ability to track and measure carbon as useful to our customers,” she said.

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