Grains on a Chessboard
Put one grain of rice on the first square, two on the next, then four, doubling each time. See where the count outgrows imagination.
Square 1 holds 1 grains (2⁰)
Total so far 1 grains (2¹ − 1)
The next square holds 2 grains, exactly one more than the 1 so far.
In everyday terms (assumed values)
Assuming one grain is 0.02 g, a bowl is 150 g (7,500 grains) and a bag is 60 kg (3 million grains), the total so far is
- Weight: 0.02 g
- Bowls: less than one
- 60 kg bags: less than one
How to play
Press "Next square" to fill one square; its pile is double the one before. Tap a square on the board to jump straight to it. "Auto" fills the squares one at a time by itself. The chart can switch between "Linear" and "Log". Weights and bowl counts are rough guides that assume one grain weighs 0.02 g.
Learn more
Put 1 grain on the first square, 2 on the second, 4 on the third, and so on: square n gets 2^(n−1) grains. The total from square 1 up to square n is 2^n − 1, always exactly one less than the next square will hold. The total over all 64 squares is 18,446,744,073,709,551,615 grains. This page computes it exactly and its tests check it. The weights and counts shown are assumed values: 0.02 g per grain, 150 g (7,500 grains) per bowl and 60 kg (3 million grains) per bag. Real rice varies. On the log chart each step up the axis multiplies by 10, so a number that keeps doubling becomes a straight line. On the linear chart only the last few squares stand tall and the earlier growth is invisible. A story about doubling grains on a board has been told for a long time, but where, when and by whom it began is not clear. Here it is just a way to feel how big repeated doubling gets.