The GRE is a major gatekeeper for many graduate programs and business schools, testing your skills in verbal reasoning, quantitative reasoning, and analytical writing. For many test-takers, Quant is the section that causes the most stress—and time pressure is a big reason why.
You’ll face 40 questions in 70 minutes, which gives you less than two minutes per question. That’s where mental math superpowers come in.
Mastering fast, accurate calculations can save you precious seconds—and give you a major confidence boost. In this post, we’ll break down the most effective mental math tricks for the GRE Quant section to help you move faster, think sharper, and score higher.
1. Break Down Big Numbers into Easy Chunks
You don’t always have to multiply numbers the hard way. Let’s say you’re asked to find 72². Instead of diving straight into long multiplication, break it down using the identity:
(a + b)² = a² + 2ab + b²Think of 72 as 70 + 2. So:
(70 + 2)² = 70² + 2(70)(2) + 2² = 4900 + 280 + 4 = 5184This method minimizes mistakes and keeps the math manageable. For more tricks like this, check out Magoosh’s guide to mental math.
2. Use the Rule of 10s and 5s
Need to find 10% of 150? Just move the decimal one place to the left—that’s 15. For 5%, take half of 10%, so 7.5.
Multiplying or dividing by 10 or 5 is a common task on the GRE. Master this shortcut and breeze through percentage questions. Kaplan also has a quick refresher on these techniques.
3. Embrace Approximation
The GRE often tests your ability to estimate rather than calculate. If you see a question like “What’s the square root of 91?”—you don’t need the exact number. You just need to know that it’s between 9² = 81 and 10² = 100, so a solid estimate is around 9.5.
Rounding numbers helps simplify decimals, fractions, and unwieldy calculations. Just make sure the answer choices are far enough apart before using this trick!
4. Estimate to Eliminate Wrong Answers
Estimation isn’t just about saving time—it’s a weapon for smart guessing. If you’re asked to find 27 × 14, you could round to 30 × 15 = 450. If the answer choices are 378, 402, 417, and 530, you can confidently eliminate 530.
Estimation helps you rule out extremes and narrow your focus. Manhattan Prep emphasizes this strategy in their mental math toolkit.
5. Practice with Purpose
Mental math isn’t just about knowing tricks—it’s about building muscle memory. The more you practice, the more automatic your calculations will become.
Use resources like:
- ETS GRE Quant sample questions
- Magoosh’s GRE question bank
- GMAT Club’s mental math flashcards (also great for GRE!)
Time yourself while practicing to simulate the pressure of the real test.
Bonus Tips for GRE Mental Math Mastery
Once you’ve got the basics down, level up with:
- Memorizing squares from 1–25 and cubes from 1–10
- Understanding even and odd number properties
- Using the FOIL method for quick binomial multiplication
- Spotting patterns in factors, multiples, and remainders
These shortcuts might seem small, but they add up fast on test day.
Final Thoughts
The GRE Quant section isn’t about doing long calculations—it’s about doing smart calculations. These mental math tricks can help you move quickly, avoid careless mistakes, and feel more in control of the clock.
If you’re preparing for the GRE, make these strategies part of your daily study routine. You’ll be surprised how much time you save—and how much your score improves.
💡 Want more GRE strategies? Check out:
Got a go-to mental math hack that works for you? Drop it in the comments—we’re all about sharing the brain-boosting love!