10% trick is instant
Sliding a decimal left is a built‑in shortcut: 10% of any number is just “shift left”. From there, 5% is half of that, and 1% is one more shift.
Percent hack
Mental Math Trainer — Percentages, Fractions, Squares
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Press Start to begin.
Correct0
Accuracy—
Streak0
Q / min—
Tips
- Press Enter to submit, Esc to skip.
- Decimals allow a small rounding tolerance (±0.01).
- Use “Daily Seed” to get a repeatable set for the day.
FAQ
What shows up in each topic?
Percentages: “What is a% of b?” (clean numbers on Easy).
Fractions: “What is a/b of n?” (chosen to land on integers by default).
Squares: “n2 = ?” (range grows with difficulty).
Is my data uploaded?
No. The trainer runs entirely in your browser. Bests and settings are stored locally.
About Mental Math Trainer
Mental Math Trainer is a quick, interactive way to sharpen everyday calculation skills without paper or a calculator. It generates short problems on the fly, times your answers when you choose a speed mode, and tracks your best scores locally. Whether you want a fast brain warm-up before work, a homework companion, or a simple math game for kids, this trainer turns practice into a clear, measurable challenge.
The idea is straightforward: mental math improves when you see common patterns often and learn to respond quickly. This calculator focuses on three essential topics: percentages, fractions, and squares. Percent questions teach you to estimate discounts, tips, and interest. Fraction problems build confidence with parts of a whole, like splitting a recipe or sharing a bill. Square questions strengthen number sense for everyday problem solving and algebra readiness. Difficulty levels adjust number size and complexity, so you can grow from basic practice to advanced drills.
Getting started is easy. Follow these steps to set up a session that matches your goals:
- Pick a mode: practice for a relaxed session, a 60 or 120 second speed round for time pressure, or a 10-question set for focused accuracy.
- Choose a difficulty level to match your comfort zone.
- Toggle the topics you want to include, or leave them all on for variety.
- Click play and type each answer, using Enter to submit and Esc to skip if needed.
- Review your score and best times, then adjust settings and play again.
Real-world uses are everywhere. Students use this mental math game to boost confidence before tests, adults use it to practice quick calculations for shopping and budgeting, and teachers use the daily seed option to give a class the same set of questions for fair practice. Because results are saved on your device, you can track progress over days or weeks without creating an account. If you are looking for a mental math practice tool, a quick arithmetic trainer, or a simple way to improve speed and accuracy, this calculator provides a clear path to better number fluency.
5 Fun Facts about Mental Math
Abacus users beat stopwatches
Competitive “mental” mathletes often visualise an imaginary abacus (soroban). World champions add or multiply 15+ numbers in under 10 seconds using that mental image.
Soroban mind
Squares carry a pattern
Consecutive squares differ by odd numbers: n² − (n−1)² = 2n−1. Memorising a few anchors lets you jump to nearby squares faster.
Pattern hop
Cross-multiply to sanity-check
For fractions of a whole, a quick cross-multiply check (a×n vs. b×answer) flags slips immediately—handy under a timer when digits blur.
Error catch
Break numbers into friends
Humans add fastest in chunks: 17% of 240? Take 10% (24), 5% (12), 2% (4.8) → 40.8. Decomposing beats long multiplication every time.
Chunking