What color do white and black make?
White and Black make black.

White and Black make black, #000000. That is the result in equal parts, mixing pigment rather than light - paint, ink and dye all behave this way.
Equal parts white and black · #000000
Change the ratio
Very little of a mix is ever half and half. Shifting the balance moves the result along the range between the two colours.
3 parts white, 1 part black · #000000
Equal parts · #000000
1 part white, 3 parts black · #000000
Lighter and darker
With white added - a tint · #000000
With black added - a shade · #000000
Why it works
Adding black to white makes a shade. Black absorbs across the whole spectrum, so the result keeps its hue but loses brightness and some saturation, which is how white becomes black.
Frequently asked questions
What color do white and black make?
White and Black make black, #000000. Mixed in equal parts that is the result you get with paint, ink or any other pigment.
How do I make the result lighter or darker?
Add white for a tint - here that gives black. Add black for a shade, which gives black. Add white a little at a time, because it takes far less than people expect to shift a mix.
What happens if I use more white than black?
Three parts white to one part black gives black. Reversing it to one part white and three parts black gives black instead.
Does this work the same way on a screen?
No. Screens mix light additively, so red and green light make yellow there. These results are subtractive - paint, ink, dye and pigment - which is what people mean when they ask what two colours make.