×11 and squares ending in 5
The first two, because they work on the first try. Ten minutes in, you can already do something you could not do before.
correct per minute
Mental math: old methods, new stopwatch
Doing 87 × 93 in your head is not talent: it is a four-step method plus enough repetition. Here are the 11 methods, and on top of them a stopwatch that will not let you lie.
The methods and the drills
Vedic cross-multiplication
The method that turns any two-digit product into a short sum. It is the workhorse of this pillar.
Complements and Trachtenberg
Subtractions that become additions, and big multiplications with nothing to carry. Methods you get wrong are added to your spaced review automatically.
Flash Anzan and soroban abacus
First reading the soroban at a glance, then imagining it and adding flashes. The traditional route to fast mental arithmetic, in full.
Arithmetic and 20×20 tables
Addition, subtraction, product, division and mixed, with a heatmap showing which cells of the table you own and which you dodge.
Percentages, change and conversions
The part you actually use in the street: the restaurant bill, the 18% off, the change, units and currency.
Roots, powers and fractions
Squares, cubes, non-exact roots to as many decimals as you ask for, and exact addition and product of fractions.
Weekday dates and estimation
Conway's Doomsday algorithm for any date, and Fermi estimation for orders of magnitude.
Chains and column addition
Chained operations with precedence, and the run of numbers added in a row from the championship format.
Number sense and logarithms
Estimating at a glance which group has more, without counting, and log₁₀ and log₂ for whoever needs them.
Competition
The championship formats, stopwatch included
You do not have to compete to use them: they are the most honest way to know where you stand, because the rules are fixed and the mark compares to your own from last week.
Big multiplication
Up to 8×8 digits, the Mental Calculation World Cup format. Start small and grow the size.
Column addition
Several numbers in a row, against the clock. The fastest way to find out whether your base arithmetic holds.
Mental marathon
A timed mixed exam across everything you have trained. It is the endurance test of this pillar.
Chained championship
Several disciplines back to back with a combined score, the way a real contest runs.
Your own records
Every discipline keeps your best mark and its history, so the comparison stays with yourself.
And the same in memory
The memory pillar has its own championship with the IAM disciplines: digits, binaries, speed cards, names.
01
The Path: doing it without paper
The Mental Math Path goes from zero to human calculator in short lessons: one method per lesson, one worked example, and drills until it comes out. You do not advance a node by reading it — you advance by solving it.
02
The Ladder: the difficulty climbs for you
The Math Ladder chains five blocks per rung — mixed arithmetic, methods, big multiplication, percentages — into one continuous session of a few minutes. You climb on your average accuracy, not on enthusiasm. And the routines by level run from basic with no clock to competition loads, so you pick how much you want to suffer today.
Fifteen minutes. Today.
The first number you'll see is your own, untrained. It's the only one you need to start comparing yourself to yourself.
The standalone drills are free. The Paths have a 14-day trial.