NumberSense
NumberSense's cast carries the estimation posture: confidently approximate first, calculate second. An estimate-first advocate, a question-flipper, a per-something specialist, and a make-10 / place-value specialist.
Level 1
Daily Estimate
The heart of NumberSense: read a real-world prompt, lock in a gut estimate before you calculate, then work out the answer and see how close you were. Estimating first is what builds number sense.
1092 real-world prompts across ratios, area, probability, fractions, big numbers, unit conversions, and mental arithmetic.
Your calibration
Do you guess high or low? Are your estimates getting closer over time? Which kinds of numbers do you already feel best? Your calibration card builds as you play — on this device only.
See my calibration → Number Line
Place a number on an open line from 0 to 100 or 0 to 1000, then reveal exactly where it belongs and how close you were. Trains the mental map that underlies all estimation.
Place numbers on the line → Mental Math Dojo
First choose the strategy the numbers are begging for — make ten, compensation, split by place, or use a double — then work it out. Flexible strategy choice is number sense.
Enter the dojo → Subitizing Flash
Dots flash for a second, then hide. Name how many you saw — without counting. Seeing quantities in groups is the foundation of fast, confident number work.
Flash the dots → 
Meet the cast — the characters who teach this
Each one stands for an idea you’ll practice. Tap a character to read their illustrated story and hear their audio drama.
Privacy & how it works
