AS vs A Level: What’s the Difference?

If you’re choosing your sixth form/college subjects, you might be wondering: what exactly is the difference between AS and A Levels? Do they link together? And, most importantly, how do they affect your university choices? You’re far from alone in asking these questions.

Since the 2015 GCSE, AS and A Level reforms in England (opens in a new tab), the relationship between AS and A Levels has changed a lot. That’s left many students (and even some parents) confused about how these qualifications work. 

This guide will give you clear answers. By the end, you’ll know exactly what each qualification involves, how they’re graded, and when you might choose one over the other.

Quick Overview: AS and A Level Defined

Let’s start with the basics, and define what the two qualifications are.

AS Level (Advanced Subsidiary) is a one-year qualification, usually taken in Year 12. You sit exams at the end of the year. It’s now a standalone qualification, meaning it doesn’t contribute to your final A Level grade.

A Level (Advanced Level) is a full two-year course (Years 12 and 13), combining the year 12 AS Level content with the year 13 A Level content. It covers more material, goes into greater depth, and ends with exams in Year 13.

Both qualifications are part of the UK’s Level 3 qualifications (opens in a new tab) (alongside BTECs and Cambridge Technicals). But A Levels are the typical standard that universities base offers on. 

Learn more about A Level Equivalents and Alternatives in our guide.

Key Differences Between AS and A Levels

Here’s a clear side-by-side breakdown, which should help you on your way to choosing your AS and A Level subjects.

Length and Study Time

• AS Level: One year (Year 12 only). Ideal if you want to explore a subject without committing two years.

• A Level: Two years (Years 12 and 13). Designed to build depth and advanced knowledge.

So, for example, a student might take four subjects in Year 12, drop one as an AS after exams, and continue with three A Levels into Year 13. This is the most typical route, one which I myself took when I was at college.

Course Content and Depth

• AS Level: Usually covers the first half of the A Level course. Topics are foundational, designed to give you a solid grasp of key principles.

• A Level: Goes much deeper, with advanced topics, extended essay-style questions, and complex analysis.

In AS Biology, you might study cell structure, enzymes, and exchange systems. At A Level, you’d then move into gene expression, energy transfer, and ecosystems, which are more advanced concepts that demand critical evaluation.

Assessment and Grading

Since the reforms, both qualifications are linear. You take all exams at the end, with no January modules or “resits” along the way.

• AS Level: Exams at the end of Year 12. Graded A–E.

• A Level: Exams at the end of Year 13. Graded A*–E.

For example, if you take AS Maths, you’ll sit two papers in Year 12. For A Level Maths, you’ll sit three longer papers at the end of Year 13, including applied modules (Mechanics and Statistics).

UCAS Points and University Applications

Put simply, the UCAS Tariff (opens in a new tab) is a points system that lets universities compare different qualifications on the same scale.

Instead of always asking for three specific A Level grades, some courses set a points target — that means you could reach it in different ways. For example, through A Levels, the International Baccalaureate, or a BTEC. It’s a flexible way of showing that there’s more than one route to meeting the entry requirements.

Here’s how AS and A Levels compare in the UCAS Tariff points system:

How universities see them:

A Levels are what your university offers are based on (e.g. “AAA” or “BBC”). AS Levels can add value but are seen as supplementary evidence, rather than core qualifications.

Some universities may look at strong AS grades as proof of academic ability, especially if you’re applying for competitive courses. But, they will not replace the need for three full A Levels.

Do AS Levels Count Towards A Levels?

Here’s the big myth: many students think an AS Level is “half an A Level.” That used to be true before 2015. Before 2015 reforms, AS exams counted for 40% of the final A Level. Post 2015, the qualifications were “decoupled” (opens in a new tab). Meaning, now, AS is entirely separate — the grade you get at AS doesn’t contribute to your A Level result.

If you take AS Chemistry and then go on to the full A Level, you’ll study some of the same Year 12 topics again, but your AS exam grade won’t transfer. You’ll sit new, separate exams at the end of Year 13.

Why Take an AS Level?

So, if AS Levels don’t count towards A Levels, why take them at all? Here are the main benefits.

Trial a Subject Before Committing

One of the biggest advantages of AS Levels is the freedom to explore. Think of them as a “trial run” to experience a subject in depth for a year without having to commit two full years of study.

This is especially useful if you’re not 100% sure which subjects you want to carry through to A Level. You might start with four subjects in Year 12, then take exams in all of them at the end of the year. From there, you can make an informed choice about which three to continue into Year 13.

Imagine you’re torn between A Level Psychology and A Level Sociology. By taking both at AS, you get a full year to discover what the lessons are like, the kind of essays you’ll need to write, and which subject suits your learning style. At the end of Year 12, you can confidently continue with the one you enjoyed most as a full A Level.

This approach takes the pressure off your Year 11 subject choices. Instead of making a big decision up front, you give yourself space to explore and refine your interests. That way, you’ll head into Year 13 with a subject combination that matches your strengths and ambitions.

Find out what A Level subjects there are to choose from.

Keep Options Open

If you’re still weighing up different degree or career paths, an AS Level can be a smart way to keep your options open. It adds extra breadth to your subject mix, showing that you’re willing to stretch yourself academically and explore more than the minimum three A Levels.

This is particularly useful if you’re interested in a wide range of courses and aren’t quite ready to narrow things down.

Say you’re thinking about Engineering, but you also have a genuine interest in Economics. By taking an AS in Economics alongside your STEM A Levels, you can keep your options open. If you later decide to apply for a joint honours degree, a degree with a business focus, or even change direction completely, your AS Economics will demonstrate you’ve studied beyond the core sciences.

Universities often value this kind of breadth because it shows curiosity and versatility — qualities that are especially appealing in competitive applications. And even if you don’t end up applying for a course related to your AS subject, it still reflects positively on your academic profile.

If you need help deciding A Level combination for your future, check out our guide on the best A Level combinations (and the worst).

Strengthen Your University Application

Even though AS Levels don’t usually form part of your official university offer, they can still add weight to your application. Admissions tutors may view them as extra proof of academic strength, showing that you’ve gone beyond the bare minimum.

An AS also highlights qualities universities value: curiosity, independence, and commitment. Taking on an extra subject demonstrates that you’re motivated and willing to challenge yourself.

A Medicine applicant with Biology, Chemistry, and Maths might add AS Psychology. While not essential, it signals an interest in the human mind and behaviour, something admissions tutors could pick up on during an interview. 

Similarly, a History applicant with full A Levels in History, English Literature, and Politics might take AS Religious Studies, showing wider engagement with the humanities.

In short, an AS won’t replace strong A Level grades, but it can give your application an edge by painting a broader picture of your skills and interests.

Frequently Asked Questions

Can I take an AS Level without taking the full A Level?

You can take an AS Level without taking the full A Level. AS is now a standalone qualification, as of 2015. You don’t need to continue it into Year 13 if you don’t want to.

Will universities accept AS Levels on their own?

For entry, universities will not accept AS Levels on their own. Universities may “note” your AS, but they base their offers on three full A Levels (or equivalent, like a BTEC).

Are AS Levels harder than GCSEs?

AS Levels are harder than GCSEs. The step up in content, analysis, and workload is noticeable. However, they’re less demanding than full A Levels since the content is narrower. Think of them as an important bridge between GCSE and A Level.

Final Thoughts

So, what’s the real difference between AS and A Levels? Well,

• AS Levels: One-year courses. Good for testing subjects, showing extra breadth, and supporting your application.

• A Levels: Two-year courses. The main qualifications that universities use to make offers.

If you’re aiming for university, your focus should be on securing strong A Level grades. But, AS Levels can play a useful supporting role, helping you explore subjects, keep doors open, and add to your academic profile.

Both qualifications are achievements in their own right. The best choice is the one that aligns with your strengths, interests, and future goals.

We have plenty more free guides about A Level choices to help you on your academic journey. Once you start them, use Save My Exams A Level revision resources – including revision notes, exam questions and mock exams – to get the best grades possible. 

References

• Get the facts: AS and A level reform - (opens in a new tab)GOV.UK (opens in a new tab)

• AS and A level decoupling: Implications for the maintenance of AS standards (opens in a new tab)

• UCAS Tariff Points - what are they and how do they work? (opens in a new tab)

• What qualification levels mean: England, Wales and Northern Ireland - (opens in a new tab)GOV.UK (opens in a new tab)