Enhanced ACT vs Legacy ACT: What Actually Changed in 2025
Bikash Roy
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Bikash personally verifies every calculator against official standards (WHO, NIH, government data). Online research specialist, SEO strategist, and web developer with 10+ years building accurate digital tools.
Full bio →Why This Distinction Matters for Your Score
If you or someone you’re comparing scores with tested before or after 2025, you’re potentially looking at two different Composite formulas — not just a different test date. This guide breaks down exactly what changed, so the ACT score calculator’s Enhanced/Legacy toggle makes sense.
The Rollout Timeline
Per ACT’s own materials, the Enhanced ACT rolled out online starting April 2025, with the paper version following in September 2025. According to ACT’s global test enhancements page, all students testing from September 2025 onward receive the new Composite Score format.
The Core Change: Science Left the Composite
Under the Legacy format, every ACT Composite was a four-section average: English, Math, Reading, and Science, each weighted equally. Under the Enhanced format, Science became an optional section. Per ACT’s own site, the science and writing sections are optional and do not affect your Composite score — the Composite is now purely a three-section average of English, Math, and Reading.
What Happens If You Take Science Anyway
Science remains available as an optional section under the Enhanced ACT. If taken, it’s scored on the usual 1-36 scale and reported on your score report — but instead of factoring into the Composite, it combines with your Math score into a separate STEM Score. Colleges that specifically want to see Science performance (some STEM-focused programs) can still see it; it just no longer moves your headline Composite number up or down.
Formula Comparison
Enhanced ACT (2025+):
Composite = (English + Math + Reading) ÷ 3
Legacy ACT (pre-2025):
Composite = (English + Math + Reading + Science) ÷ 4Both formulas use the same rounding rule — ACT’s “round half up” convention — but averaging three numbers instead of four changes how much any single section score moves the final Composite. Under Enhanced, each section carries roughly 33% weight; under Legacy, each carried 25%.
Why This Matters When Comparing Scores
A 29 Composite from a 2023 Legacy test and a 29 Composite from a 2026 Enhanced test represent averages of different numbers of sections, weighted differently — they’re not calculated the same way, even though the number itself looks identical. If you’re comparing your own retake scores across the 2025 transition, or comparing scores with someone who tested under a different format, that context matters. The ACT score calculator’s format toggle exists specifically so you can calculate either version correctly rather than assuming they work the same way.
What Didn’t Change
The 1-36 scoring scale for individual sections, the “round half up” rounding rule, and the fundamental purpose of the Composite as colleges’ primary reference number all carried over unchanged from the Legacy to the Enhanced format. The redesign changed which sections count toward Composite, not the underlying scale or rounding logic.
Applying This to Your Own Scores
If you’re unsure which format your score report reflects, check the test date — September 2025 onward is Enhanced; earlier is Legacy. Enter your section scores into the ACT score calculator using the matching toggle, and see ACT Composite worked examples for both formulas calculated side by side.