The overall percentage is produced by a defined sequence: credits within a category, a category percentage, a category weighting, a summed total, a benchmark comparison and a separate minimum-standards check.
BREEAM, a registered trade mark of BRE, calculates an overall assessment result by combining performance across environmental categories. The scheme does not treat every achieved credit as having the same direct effect on the final percentage. Category achievement, category weighting, overall benchmarks and minimum standards all form part of the method.
The calculation begins with the assessment issues contained in the applicable technical standard. Each issue describes a defined sustainability outcome and the evidence needed to demonstrate it. Where the project meets the applicable conditions, the associated credits can be recognised by the licensed assessor.
Credits are therefore not informal points awarded for good intentions. They depend on documented performance under the selected standard and version. A design feature may appear environmentally beneficial but still require particular calculations, specifications, reports, drawings, records or confirmation before it can contribute to the formal assessment.
The available credits are also controlled by the method. The project team does not create additional credits, change their value or substitute a preferred criterion. Where applicability rules affect the credits available to a project, those rules are interpreted through the technical manual and the formal assessment process.
Within a category, the credits achieved are considered against the credits available. This produces the category percentage. In conceptual form, the method is the achieved credits divided by the available credits, expressed as a percentage for that category.
The category percentage shows how much of the assessable performance within that category has been achieved. It does not yet show the category's final contribution to the whole-building score. A strong category percentage may have a larger or smaller effect depending on the weighting assigned to that category under the applicable standard and country basis.
This step also explains why raw credit totals can be misleading. Credits from different categories are first interpreted within their own category structure. The method does not simply place every credit into one undifferentiated project total. Category boundaries preserve the distinction between different environmental subjects.
The category percentage is then multiplied by the relevant category weighting. The result is the weighted contribution of that category to the overall assessment percentage. A weighting expresses the relative environmental priority assigned to the category by the scheme method.
The project team does not choose the weighting to favour its strongest design areas. Weightings are set through the scheme's controlled framework and can differ between standards, versions and countries. BRE publishes pre-populated country sheets for countries where most assessments have taken place and a weightings form for new countries.
No list of weighting percentages is needed to understand the calculation. The important principle is that equal category percentages do not necessarily make equal contributions to the total. The weighting converts category achievement into its prescribed share of the overall result.
After each category contribution has been calculated, the weighted contributions are added together. Their sum produces the overall assessment percentage before the rating decision is completed. This is the headline percentage commonly associated with the assessment.
The total reflects both achievement and priority. Credits determine performance within categories, while weightings determine how those category results influence the whole. A project can therefore reach the same overall percentage as another project through a different pattern of strengths and weaknesses.
The calculation is transparent in principle but controlled in application. The assessor must use the correct standard, version, project type, country basis and applicability rules. A spreadsheet assembled from a different project or older manual can produce a plausible-looking number that has no formal standing for the current registration.
The overall percentage is compared with the rating benchmarks that apply to the selected scheme and version. In BRE's UK New Construction 2014 non-domestic technical manual, reference SD5076, Outstanding begins at 85 per cent or above, Excellent at 70 per cent, Very Good at 55 per cent, Good at 45 per cent and Pass at 30 per cent, with Unclassified below 30 per cent.
Those figures explain the benchmark step but must not be treated as universal. They are specific to that scheme and version. Other schemes and versions differ, and a calculation for a UAE international assessment must use the benchmarks belonging to its registered method.
The benchmark indicates the rating band that the overall percentage could support. It does not by itself guarantee that rating, because minimum standards form a separate gate. The calculation therefore continues beyond matching the total to a band.
Minimum standards require specified performance for particular rating levels. They are not merely extra weighted credits. A project may have an overall percentage within a higher band but still be unable to receive that band if an applicable minimum standard has not been met.
This arrangement prevents a high total from compensating for every weakness. Certain outcomes are considered necessary for the integrity of a rating, especially at higher levels. BRE stated that New Construction Version 7 introduced new minimum standards defining the expectations attached to Outstanding and Excellent.
Minimum standards should therefore be tracked independently from the forecast percentage. A project scorecard that shows only credits and a running total is incomplete. The assessment team needs to understand which minimum standards apply, what evidence demonstrates them and when decisions must be made to keep them achievable.
BRE summarises overall performance through four things acting together: the rating benchmarks, the minimum standards, the environmental section weightings, and the assessment issues and credits. Each answers a different question within the method.
The issues and credits establish what performance is recognised. The category weightings establish the relative contribution of each environmental area. The benchmarks map the overall percentage to a rating band. The minimum standards determine whether essential conditions for that band have been met.
Removing any one element distorts the result. Credit counting without weightings ignores relative priority. A weighted score without benchmarks has no rating label. A benchmark without minimum standards can overstate the available rating. A rating discussion without the underlying issues and evidence loses contact with actual project performance.
The calculation is supported by evidence rather than accepted as a self-declared project score. Qualified assessors licensed for the scheme review the project information, determine whether the applicable requirements have been met and validate the assessment submission.
BRE's published process contains five stages: appoint a licensed assessor, register the project, complete the assessment, pass through quality assurance, and receive certification. The quality audit is carried out by BRE Global Ltd. BRE Global Ltd is accredited by the United Kingdom Accreditation Service against BS EN ISO/IEC 17065:2012 and aligns its activities to ISO 9001.
The audit can examine whether the assessment has been completed in accordance with the method and whether the evidence supports the claimed credits and rating. Certification follows the scheme's quality assurance process; it is not created by an independent information website, a design team's internal tracker or an unreviewed score estimate.
Projects often use provisional score forecasts during design and construction. These forecasts can be useful for coordination, but they remain conditional. Credits may depend on design development, procurement choices, completed calculations, site records, commissioning results or final evidence.
A forecast can change when an issue becomes inapplicable, when available credits are confirmed, when a design commitment is altered or when evidence fails to demonstrate the required outcome. Version selection and country weighting basis can also affect the calculation. The formal result belongs to the registered assessment and audited evidence, not to an early planning assumption.
The five-year validity of a registration adds a programme consideration. A project that extends beyond its registration validity may face administrative consequences under the scheme process. Version 7 registrations opened in September 2025, following the launch on 30 September 2025 and a three-month transition in which Version 6 and the 2018 version could still be registered. These dates show why the calculation method must always be linked to the actual registration.
The final percentage is a weighted assessment result, not a direct physical measurement. It cannot be converted automatically into a fixed amount of energy saved, water avoided, carbon reduced or financial value created. Two projects with the same percentage can differ in location, design, category performance and operational outcomes.
The rating shown as stars on the certificate summarises where the audited result sits within the applicable scale. Pass, Good, Very Good, Excellent and Outstanding are the principal published bands, while the In-Use scheme also includes Acceptable. A result below the Pass benchmark in the UK New Construction 2014 method is Unclassified.
A sound interpretation therefore follows the calculation in order: identify the applicable issues and credits, calculate category achievement, apply the correct category weightings, sum the weighted contributions, compare the total with the correct benchmarks and verify the minimum standards. That sequence explains the method without reproducing the commercial credit tables or category weighting percentages.
Credits achieved are considered against credits available within a category, producing a percentage for that category alone.
The category percentage is multiplied by the relevant category weighting to give that category's prescribed share of the overall result.
The summed percentage is compared with the applicable rating benchmarks, and the applicable minimum standards are then checked as a separate condition.
No. Credits are first considered within their own category to produce a category percentage. That percentage is multiplied by the category weighting, and the weighted contributions are then summed to give the overall assessment percentage.
No. Minimum standards operate as a separate gate. A project may sit within a higher band on percentage alone and still be unable to receive that band if an applicable minimum standard has not been met.
Credits may depend on design development, procurement choices, completed calculations, site records, commissioning results or final evidence. The formal result belongs to the registered assessment and the audited evidence, not to an early planning assumption.
This is an independent information resource. It is not affiliated with, endorsed by, or connected to BRE. BREEAM and BRE are the trademarks of their respective owners and are used here only to identify the scheme described.