TLDR

• Covers all essential AP Biology equations: water potential, Hardy-Weinberg, chi-square, Gibbs free energy, population growth, and more.

• Organized unit by unit with variable definitions for clarity.

• Designed as a one-page printable PDF for fast reference.

• Includes constants, statistical formulas, and tutor tips for exam day.
  👉 Download the Free AP Biology Formula Sheet (PDF) above

Introduction

The AP Biology exam often requires you to apply formulas to experimental data and population models. Whether it’s calculating water potential, testing genetic ratios with chi-square, or modeling population growth, these equations can quickly add points to your score if you know them well.

That’s why we created this free one-page AP Biology Formula Sheet — a simple, printable PDF that puts every important formula in one place.

AP Biology Formulas by Unit

Unit 1: Chemistry of Life

• Water Potential: Ψ = Ψs + Ψp

• Solute Potential: Ψs = -iCRT

• Surface Area to Volume Ratio: SA:V = Surface Area / Volume

Unit 2: Cell Structure and Function

• Surface Area to Volume Ratio (applied to transport efficiency)

• Rate of Diffusion: Rate = Distance / Time

Unit 3: Cellular Energetics

• Gibbs Free Energy: ΔG = ΔH – TΔS

• ATP Yield: ~36–38 ATP (aerobic), ~2 ATP (anaerobic)

• Enzyme Reaction Rate: Rate = ΔProduct / Δt

Unit 4: Cell Communication and Cell Cycle

Note: No unique equations introduced in this unit.

Unit 5: Heredity

• Probability Rules:

  • Multiplication Rule: P(A and B) = P(A) × P(B)

  • Addition Rule: P(A or B) = P(A) + P(B) – P(A and B)

• Chi-Square: χ² = Σ (O – E)² / E

• Degrees of Freedom: df = categories – 1

Unit 6: Gene Expression and Regulation

Note: No unique equations introduced in this unit.

Unit 7: Natural Selection

• Hardy–Weinberg: p + q = 1 and p² + 2pq + q² = 1

• Relative Fitness: w = (offspring of genotype) / (offspring of most successful genotype)

Unit 8: Ecology

• Exponential Growth: Nt = N0 * e^(rt)

• Logistic Growth: dN/dt = rN (1 – N/K)

• Mark–Recapture: N = (M × C) / R

• Photosynthesis / Respiration Rate: Rate = ΔO2 / Δt or ΔCO2 / Δt

• Net Productivity: NPP = GPP – R

Statistics and Data Analysis

• Standard Error: SE = s / √n

• Confidence Interval (95%): x̄ ± (1.96 × SE)

Why This Formula Sheet Matters

Formulas are a smaller part of AP Biology compared to free-response questions, but they’re also some of the easiest points to secure. The key is not just memorizing them, but knowing when to apply them.

💡 Tutor Tip: Our Johns Hopkins tutor says, always highlight what the question is asking. Then pick the formula that matches, this saves time and prevents small mistakes.

Looking for more than just a formula sheet? Our Ivy-League tutors specialize in AP Biology and know how to turn these equations into higher scores.

📌 Book a free AP Biology strategy session today