Topic
Measurement
The math you actually use. Length, time, weight, volume — and the units that turn raw numbers into real quantities.
Measure twice
Measurement turns numbers into things you can see, feel, and use. A meter is a length you can hold; a kilogram is a weight you can lift; a minute is a duration you can wait through.
Introduction to measurement
What you can measure: length, mass, capacity, time, temperature.
What is a unit?
A standard chunk you compare other things against — and why standards matter.
Length
mm, cm, m, km — and inches and feet.
Metric length
mm, cm, m, km — base 10, easy to convert.
US customary length
Inch, foot, yard, mile — and the conversions you really need.
Time
Read clocks, count minutes, work with durations.
Days, weeks, months, years
How many days in this month? When does the leap year fall?
Months
Twelve months, names and origins — and how many days each one has.
Weeks
Seven days, where the names come from, and how the modern week was set.
Days
Sunrise to sunrise — and the 24 hours in between.
Years
One trip around the sun — and why it's not exactly 365 days.
Seasons
Spring, summer, autumn, winter — and the tilt of the Earth that drives them.
Time units convert
Seconds, minutes, hours, days — convert between any two.
Stopwatches & timers
Measuring elapsed time — for races, recipes and physics experiments.
Analog & digital clocks
Two ways to display the same time — read either at a glance.
Calendar — leap years
Why every fourth year — except some — gets an extra day.
Compass — N, S, E, W
Direction by the four cardinal points — and the in-between bearings.
Weight & volume
Grams, kilos, liters — feel the size.
Weight vs mass
Mass is how much stuff. Weight is how hard gravity pulls — different things.
Apparent weight
Why you feel heavier in a lift going up — gravity hasn't changed.
Metric mass
Milligrams, grams, kilograms, tonnes — base 10, easy to scale.
Metric volume
Millilitres to litres — and a litre is a cube 10 cm on a side.
Measuring cups
Cooking conversions — cups to tablespoons to millilitres.
Cooking measurements
tsp, tbsp, cup, fl oz — the units a kitchen actually uses.
Metric area
Square metres, hectares, square kilometres — measuring land in metric.
Metric speed
Metres per second, km/h — and how to convert between them.
Metric acceleration
m/s² — how fast speed itself is changing.
Temperature
Celsius ↔ Fahrenheit. Drag the thermometer to flip the scale.
Thermometer
How a thermometer reads heat — liquid expansion, electrical, infrared.
Speed & velocity
Distance ÷ time. Drag the slider, watch the speedometer climb.
Unit conversions
Metric ↔ imperial — for length, mass, volume and area.
Unit conversion method
Multiply by a fraction equal to 1 — units cancel like factors.
Imperial / metric conversion
Inches to cm, pounds to kg, miles to km — the chart you always need.
US standard units
Length, mass, volume — the units you actually grew up with in the US.
Area conversions
Square metres, hectares, acres — the math of land.
Volume conversions
Litres, gallons, fluid ounces — pour units between systems.
Length conversions
Convert any length — metric to imperial, ancient to modern.
Accuracy & precision
Same target every shot? Or close to bullseye? They're different things.
Error in measurement
Every measurement has uncertainty — quantify it, report it, propagate it.
Estimate distance
Eyeball a length — and check how close your guess was.
Lengths small to large
From an atom to the universe — every length, on a log scale.
The metric system
Why every unit is built on tens — and why the world adopted it.
Metric prefixes
Kilo, mega, giga, milli, micro, nano — powers of ten with friendly names.