Measure What Matters: Software's Carbon Impact
Every software application has a carbon footprint through the energy it consumes and the hardware it requires. The Software Carbon Intensity (SCI) specification provides the first ISO-accredited methodology to measure this impact as a score.
Developed with consensus from GSF member organisations
What is Software Carbon Intensity?
The Software Carbon Intensity (SCI) specification is an ISO-accredited standard (ISO/IEC 21031:2024) for measuring the carbon emissions of software applications. It provides a clear, consistent methodology that transforms complex environmental data into a single actionable score — making it possible to compare different software solutions, track improvements over time, and make evidence-based decisions about technology choices.
Unlike traditional carbon accounting that focuses on totals and offsets, SCI calculates a rate — carbon emissions per functional unit of your software, whether that's per user, per transaction, or per API call. This approach reveals the true efficiency of your software and guides you toward meaningful reductions through better code, smarter infrastructure choices, and carbon-aware computing strategies.
Why SCI Matters
Software's environmental impact is invisible but significant — and growing exponentially with AI and digital transformation.
Industry Impact
Every line of code, every server, every user interaction contributes to the software's growing carbon footprint. The SCI specification makes this invisible impact visible and actionable. By providing a standardised measurement protocol, it enables the entire industry to work from the same playbook — creating transparency, driving innovation, and accelerating the transition to truly sustainable technology. Major organisations, including AVEVA, Microsoft, NTT DATA, and UBS, are already using SCI to transform how they build and deploy software.
Business Benefits
Drive Cost Efficiency - Software optimised for lower SCI scores uses less energy and hardware, directly reducing operational costs
Meet Sustainability Goals - Demonstrate measurable progress toward net-zero commitments with ISO-certified methodology
Gain Competitive Advantage - Differentiate your products with verified sustainability credentials that customers increasingly demand
Future-Proof Operations - Stay ahead of emerging regulations and reporting requirements with established measurement practices
Environmental Impact
Every point reduction in your SCI score represents real carbon that never enters the atmosphere. This isn't about purchasing offsets or making claims — it's about fundamental changes in how software is designed, developed, and deployed. When organisations optimise for SCI, they naturally adopt practices that reduce energy consumption, extend hardware lifecycles, and shift computing to cleaner energy sources. The cumulative effect of thousands of development teams making these optimisations could prevent millions of tons of carbon emissions annually.
A New Way to Think About Software
The SCI score combines three essential factors that determine software's carbon footprint: the energy your software consumes (E), the carbon intensity of that energy based on location and time (I), and the embodied emissions from manufacturing the hardware (M). These are calculated per functional unit (R) — creating a rate that reveals true efficiency.
SCI = (E × I + M) per R
E — Energy
Energy consumed by your software across all infrastructure — servers, storage, networking, and end-user devices.
I — Carbon Intensity
The carbon intensity of the energy used, varying by location and time — enabling carbon-aware scheduling and deployment.
M — Embodied
Embodied emissions from manufacturing the hardware your software runs on, amortised over its expected lifespan.
R — Functional Unit
A unit of work meaningful to your software — per user, per transaction, per API call — that turns totals into a rate.
This simple equation transforms how teams approach software development. Instead of guessing at environmental impact, you can measure it. Instead of generic best practices, you have specific targets. Instead of greenwashing, you have genuine reductions.
Organisations Leading with SCI
Financial institutions, consultancies, and technology companies worldwide are implementing SCI to measure and reduce software carbon emissions.
Implementing SCI to Track Software Emissions
Accenture applied SCI to calculate and track carbon emissions for an internal reference application, establishing a practical baseline methodology that includes embodied emissions.
Baselining Software Carbon Emissions
UBS demonstrates applying SCI to baseline carbon emissions for two enterprise applications in investment banking and asset management, identifying available data sources and calculation methodologies.
Decarbonizing Software with SCI
CAST integrated SCI with CAST Highlight to decarbonize an enterprise application, achieving an estimated 400 kg annual CO2 reduction and 5% improvement in execution duration.
Calculating Carbon Footprint for Serverless Apps
A practical guide to measuring carbon emissions of serverless applications using the SCI specification, with step-by-step methodology for event-driven architectures.
Carbon-Aware Computing at UBS
UBS and Microsoft implemented the first enterprise-scale carbon-aware computing system, using SCI and the Carbon Aware Software Development Kit (SDK) to reduce emissions in their core risk platform workloads.
“SCI specification provided a practical methodology to baseline carbon emissions of the application, including embodied emissions and reducing the same.”
Validated by Academia and Industry
The SCI specification is the only ISO-accredited carbon measurement standard for software, referenced in 15+ peer-reviewed research and implemented by leading technology organisations worldwide.
Microsoft Azure Sustainability Framework
Microsoft integrated SCI into Azure's official sustainability framework.
Read Documentation →ThoughtWorks Implementation Guide
Global implementation guide for calculating software carbon intensity.
Read Guide →ACM Symposium on Cloud Computing (SoCC '24)
The Sunk Carbon Fallacy: Rethinking Carbon Footprint Metrics for Effective Carbon-Aware Scheduling.
Read Paper →Built for Every Role in Software
Everything You Need to Get Started
The SCI Specification
Access the complete ISO/IEC 21031:2024 standard with technical methodology and implementation guidance.
SCI Guidance
Explore various approaches on how to understand the different methodologies available for calculating the core components of the SCI.
Get Involved
Help Shape the Future of Software Carbon Measurement
Journey to Transformation
Current focus: The specification is actively developing, and experts, operators, and sustainability practitioners are invited to refine and validate it.
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June 2021
Vision Launched
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March 2022
v1.0 Published
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April 2024
ISO Accreditation Achieved
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October 2024
v1.1 Released
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2026
Current
Get Involved
Help Shape the Future of Software Carbon Measurement
Related Articles
News, insights, and updates about the Software Carbon Intensity standard.
Establishing Software Carbon Transparency: Why We’re Exploring SCI Disclosure Certification
At GSF, we’re exploring a voluntary, structured approach to self-reported SCI disclosure, designed to build shared knowledge base needed for meaningful, measurable progress. Learn about its potential impact.
Calculating Your Carbon Footprint: A Guide to Measuring Serverless App Emissions on AWS
Denis Angeletta and Franziska Warncke explain how NTT Data applied the SCI specification to quantify the carbon emissions of serverless applications.
Software Carbon Intensity (SCI) Specification Achieves ISO Standard Status, Advancing Green Software Development
The ISO confirms that the SCI Specification is a reliable, fair, and comparable protocol for measuring and reducing software's carbon footprint, achieving a major milestone in green software.
Decarbonizing Software: How CAST applied the SCI Metric to Make a Difference
“The automatically generated Green Software Insights from CAST Highlight enabled us to identify exactly where in our code we could improve our green impact and then estimate the actual CO2 emissions savings with concrete numbers.” - Michael Muller, Director Product Management, CAST
Baselining Software Carbon Emissions - A Use Case by UBS
Using the SCI specification, UBS compares two banking applications with regard to their carbon emissions.
How Accenture Implemented the SCI Specification Score to Track Software Emissions
An in depth look at how Accenture implemented the SCI Specification Score to track software emissions.
Texas State University deems GSF SCI an effective metric to evaluate the carbon impact of software
The Texas State University has just released its report on a study evaluating software carbon intensity of foundation models. Among other findings, the study confirms that the SCI is suitable for effectively measuring the carbon impact of software.
Software Carbon Intensity (SCI): Crafting a Standard
The Software Carbon Intensity (SCI) standard provides an actionable approach to designers, developers and deployers of software systems to measure the carbon impacts of their systems.