How to play · 7 min read
How to Solve the 24 Game: Strategies and Examples
Aim for 3 × 8, 4 × 6 or 2 × 12, then work backward. Worked examples, the 16 sets that need a fraction like 3 3 8 8, and exact counts from all 1,820 sets.
A little practice. A sharper game.
Free brain training: mental math, memory and speed
Dual N-Back, Flash Anzan, mental math and reaction time. Your first score in about 30 seconds.
Play now, free
13 free games, 8 without an account
Choose your workout
Not sure? Start with Reaction Time or Mental Arithmetic.
Reflex
Reaction Time
Wait for green. Tap. See your milliseconds.
2 minPlay
Mental math
Mental Arithmetic
Multi-step problems, nothing but your head.
4 minPlay
Mental math
Math Chain
3 minFree account
Mental math
Missing Operator
3 minFree account
Working memory
Flash Recall
3 minFree account
Reflex
Time Sense
1 minFree account
Mental math
Blink and Add
4 minFree account
Today's challenge
10 questions. About a minute. Same for everyone.
Worth up to 60 XP today. Daily Challenge streaks multiply XP; freezes save a missed day.
Your rank
The fox’s journey
Ten ranks from Curious Kit to Legendary Fox. Every finished game and Daily adds XP.
Start as a Curious Kit
A free account starts with a one-time +500 XP welcome bonus, enough for Pattern Tracker.
Curious Kit
0- 2Number Scout
100 - 3Sum Seeker
250 - 4Pattern Tracker
500 - 5Abacus Adept
1,000 - 6Memory Weaver
2,000 - 7Swift Calculator
3,500 - 8Mind Ranger
5,500 - 9Grand Reckoner
8,000 - 10Legendary Fox
12,000
From the blog
All articlesResearch & scores · 4 min read
Find the Odd One Out: Why Similar Letters Slow Your Search
Spotting an X among Os is instant. Spotting an O among Qs is slow. What visual search research says about similarity and grid size, and how to scan faster.
Research & scores · 4 min read
Average Reaction Time: What 255 Runs on HumanCalc Show
The median run on HumanCalc's 5-tap reaction test is 283 ms. Desktop runs come in near 257 ms and phone runs near 306 ms. Full spread and what shifts a score.
How HumanCalc works
- Levels that move with you
- Three right answers in a row move you up a level; misses move you down. Every game page shows how far real players get.
- Built on real test tasks
- Dual n-back, the Stroop test, paced serial addition and flash anzan come from cognitive research. Each game page names its source.
- Honest about the evidence
- Practice reliably makes you better at the task you train. Whether that carries over to everyday memory is debated, and we say so.
- 13 games, all free
- 8 run without an account. A free account saves your scores, streak and XP, and unlocks the other 5.
Questions people actually ask
Does brain training actually work?
It reliably makes you better at the task you train. Broader transfer, to intelligence, everyday memory or work, is genuinely contested, with strong studies on both sides. We cite the source behind each game rather than promising outcomes.
How long until I see results?
There is no fixed timeline. Compare your accuracy and scores across repeated sessions, rather than judging one attempt. Getting better at a game does not by itself show broader cognitive improvement.
Is HumanCalc free?
Yes, every game is free to play. No subscription, no trial, no paywalled levels. Optional coin packs only buy cosmetics and streak recovery, and never add XP or change a ranking.
Do I need an account?
Dual N-Back, Flash Anzan, Mental Arithmetic, Serial Addition, Reaction Time, Stroop Test, Odd One Out, and Make 24 are open to everyone. A free account unlocks Math Chain, Missing Operator, Flash Recall, Time Sense, and Blink and Add, and saves your progress across devices. All games are free.
How often does the leaderboard reset?
Every week. A short season rewards steady training without turning into a permanent grind.
Pick a game and start.
Start with a guest game, or make a free account to unlock the rest. Every game is free, with no download or subscription.
Choose a game