Learn math by touching it
Dot Decimal is a math notepad. Write a worksheet, then drag a number and watch every answer, curve and surface move with it. Intuition grows as you play.
Things a spreadsheet can't show you
Every number, point and slider is connected to the lines that use it. Change one and watch the rest respond. Try it here.
Drag a corner. Watch the area change.
Points are variables, so the polygon is too. Move any corner and its coordinates, area and perimeter update on the lines below. In the app you can also see the shoelace, triangle and Pick's theorem methods drawn on the same shape.
Add terms. See the approximation close in.
A slider is one line: n = 4 in 0 … 10. Drag it and the Taylor polynomial is rewritten and plotted again. The shaded band shows where it stays within 0.1 of eˣ.
Drag a number, or Option-click it for fine control.
Drag any number sideways to change it. Hold ⌥ while you drag for finer steps, or ⇧ for bigger ones. On a Mac, Option-click a number to open a precise slider with − and + buttons and a choice of step size. Every answer that uses the number updates as you go.
On iPhone and iPad, drag a number sideways.
A matrix is a way to move the plane.
Drag the tips of î and ĵ to edit the matrix. The grid bends with them, and the shaded square shows the determinant as an area. It turns orange when the plane flips over.
Spin a surface to see its shape.
One line draws a surface in 3D with Swift Charts. Drag it to turn it around and look at peaks, valleys and saddle points from any side. Pick another function to compare.
A calculator that reads like your notes
Type it the way you'd write it on paper. Dot Decimal works out the units, times, places and money.
Units
3.2 m * 2.4 m7.68 m²line1 in ft²82.667 ft²Times and time zones
9am PST in GMT5:00 pm9:30am + 4h 48m2:18 pmCalculus
integral(sin(x), x, 0, π)2derivative(sin(x), x)cos(x)Algebra
solve(x²-5*x+6, x)x = 2, x = 3factor(x³-6*x²+11*x-6, x)(x − 1)(x − 2)(x − 3)Matrices
det([2, 1; 1, 3])5eig([2, 1; 1, 2])λ = 3, 1Money and big numbers
$320k * 6.5%$20,8003 million * 1.13.3MFor programmers
0x9F31 to decimal40,75324px in rem1.5remPlaces and weather
distance Detroit to ChicagoApple Mapssunset in DetroitApple WeatherPlots
plot(sin(x), x, -π, π)2Dplot3d(sin(x)*cos(y), x, -π, π, y, -π, π)3DYour sheets, on all your devices
Turn on iCloud sync and every sheet you write shows up on your Mac, iPad and iPhone, right where you left it.
Real-world numbers, right in your sheet
Live stock prices, weather, energy prices, food and nutrition, and labor statistics. Use them like any other number.
Start from a working sheet
Every example is a real Dot Decimal sheet. Download it, open it, and drag things until the idea makes sense.
Projectile
Range, peak height and the area under the arc. Drag the angle to find the longest throw.
range = v₀²*sin(2*θ)/g TrigonometryWaves
Four sliders for amplitude, frequency, phase and offset, and an integral with bounds you drag.
f(x) = a*sin(b*x+c)+d FinanceMortgage
Monthly payment, total paid and total interest on a $320k loan at 6.5% over 30 years.
payment = loan*monthly rate/…Free on Mac, iPad and iPhone
Every math feature is free, on every device.
macOS 26, iPadOS 26 and iOS 26 or later