ACT Science Guide: Who Should Take It and How to Ace It

On the enhanced ACT, science is an optional add-on, just like writing. Your composite (1–36) is the average of English, math, and reading only, so science can't raise or lower it.

If you add science, you get two extra numbers on your score report:

• A science score (1–36).
• A STEM score: the rounded average of your math and science scores.

Adding it also adds 40 minutes to your test day. Check ACT's fees page for current pricing, including any cost for add-ons.

Take it if…

• Any college, program, or scholarship on your list asks for the science or STEM score. This is the only reason that's close to mandatory. Check each school's testing policy page. Policies differ, so don't rely on what a friend's school does.
• You're applying to STEM majors and want to show quantitative reasoning beyond math.
• You're good at it. If your science practice scores match or beat your English/math/reading level, a strong science and STEM score is an extra positive signal.

Skip it if…

• None of your schools or scholarships ask for it, and
• you'd rather spend your prep time on English, math, and reading, the sections that actually build your composite, or
• an extra 40 minutes of testing would wear you out before you finish.

40 questions in 40 minutes (34 scored, plus unmarked field-test questions), so about one minute per question. No calculator: calculators are allowed only on the math section. The math you'll need is estimation, simple ratios, and reading values off graphs.

The takeaway: this is mostly a reading-data-under-time-pressure test, not a memorize-the-textbook test. Most answers are on the page. A few questions may assume basics you learned in class, like what a control group is or that water boils at 100°C at sea level.

Research Summaries (about half the test)

Before any numbers, find what changed and what stayed the same in each experiment. Write it in the margin or your scratch notes: "Exp 1: temp varies, salt = 0. Exp 2: salt varies, temp = 25°C." Half the questions are about exactly that.

Data Representation

Read titles, axis labels, and units first, then the data. Many questions are one-lookup questions if you know which figure and which axis to use. Watch for two y-axes and for curves that share a graph.

Conflicting Viewpoints

This is the one passage where you should read the text first. Summarize each viewpoint in five words or fewer ("H1: spun off Earth; H2: captured; H3: giant impact"), and note what each one predicts. Most questions ask which viewpoint a new finding supports, or what two viewpoints agree on.

1. Interpretation of Data: read what the number means

A table shows the time an enzyme takes to break down a sample at four pH values: pH 4, 80 s; pH 6, 35 s; pH 8, 20 s; pH 10, 55 s. At which pH does the enzyme work fastest?

Fastest means the shortest time, so the answer is pH 8. The trap is picking the biggest number (pH 4). When the measured quantity is a time to finish something, smaller is faster. Always ask what the number measures before comparing.

2. Scientific Investigation: variables and controls

A student tests how a pendulum's length affects the time for one swing, using four lengths, the same mass, and the same release angle. Why keep the mass and angle the same?

So that length is the only thing that changes. Then any change in swing time can be credited to length. Length is the independent variable, swing time is the dependent variable, and mass and angle are controlled variables. Expect at least one question like this on every experiment passage.

3. Evaluating models: which viewpoint does the evidence support?

Student 1 says a plant grew toward a window because of light. Student 2 says it grew toward the window because of warmth from the glass. A new trial places a cool LED lamp on the opposite side of the plant, and the plant bends toward the lamp. Which student does this support?

The lamp supplies light but not warmth, and the plant still bends toward it. That supports Student 1. The move is to find the result that separates the two explanations, not one they'd both predict.

• Pace by passage, not by question. About a minute per question means a passage with six questions gets about six minutes. If you're way over, guess, flag, and move on. There's no penalty for wrong answers.
• Go to the questions early on data-heavy passages. Many point you straight to the figure you need.
• Trend words matter. "Increases only" is different from "increases, then decreases." Check the whole range, not just the endpoints.
• Interpolate and extrapolate by following the pattern. If values climb about 2 units per step, the next one is about 2 higher.
• Units trap. mL vs. L, °C vs. K, seconds vs. minutes. The wrong-unit answer is usually among the choices.
• "Supports" is not "proves." An answer that says the data prove something is almost always too strong.
• Don't answer from outside knowledge when the passage says something different. The passage wins.
• One counterexample kills an "always" claim. If a claim says "the warmer, the lower," find any pair that breaks the pattern.

1. Days 1–2: Take a timed practice science section. Tag each miss as data reading, experiment design, or viewpoints.
2. Days 3–6: Research Summaries drills, since they're half the test. For every passage, write the "what varied / what stayed constant" line before answering.
3. Days 7–9: Data Representation speed work. Give yourself 30 seconds to name every axis, unit, and trend before reading the questions.
4. Days 10–11: Conflicting Viewpoints. Practice five-word summaries and "which finding supports which view" questions.
5. Days 12–14: One or two full timed 40-minute sections from ACT's free official practice tests. Review every miss.

Pair this with the math work in our ACT Math guide (the STEM score is math + science) and the big picture in our ACT guide.