Plinko Calculator & Fair Bounce Verifier

The deterministic path of Plinko balls

Plinko is a staple on crypto casinos such as Stake and BC.Game. Each ball drops through a grid of pegs, deflecting left or right at every row before settling into one of the multiplier pockets along the bottom.

No physics engine decides where it lands. The full trajectory is locked in the instant you press “Play,” derived from your cryptographic seeds. A provably fair Plinko verifier recomputes that bounce sequence independently, so you can see precisely how each drop unfolded.

The math: Row-by-row bounce calculations

Tracing a ball means converting raw hash output into a series of directional decisions — one float per row of the board:

1. Generating the row floats

Your seeds and nonce are combined under HMAC-SHA256. Rather than stopping after the first 4 bytes, the verifier reads consecutive 4-byte segments — one segment per row on boards of 8, 12, or 16 rows:

Float_Row_i = Hex_To_Decimal(4_Bytes_i) / 4294967296

2. Calculating Left vs Right

Each row’s float maps directly to a direction:

• Float < 0.50: **Left** (value 0).
• Float ≥ 0.50: **Right** (value 1).

3. Finding the final landing pocket

Add up every Right bounce. That sum is the landing pocket index. On a 16-row board:

Pocket_Index = Sum(Right_Bounces)

Indexes run from 0 (sixteen Left bounces, far-left pocket) to 16 (all Right, far-right).

Data Sandwich: Auditing an 8-row Plinko drop

Here’s a worked audit on an 8-row board. Your ball landed in Pocket 7 near the right edge for a healthy return. You rotated seeds and pasted them into the verifier:

• Server Seed: b4a2c8...
• Client Seed: plinko_drop_1
• Nonce: 3

Running the HMAC yields eight floats, one per row:

1. Row 1: Float 0.65 -> **Right** (1)
2. Row 2: Float 0.42 -> **Left** (0)
3. Row 3: Float 0.78 -> **Right** (1)
4. Row 4: Float 0.81 -> **Right** (1)
5. Row 5: Float 0.52 -> **Right** (1)
6. Row 6: Float 0.93 -> **Right** (1)
7. Row 7: Float 0.21 -> **Left** (0)
8. Row 8: Float 0.71 -> **Right** (1)

Adding the Right values: 1 + 0 + 1 + 1 + 1 + 1 + 0 + 1 = 6.

Six Rights, two Lefts — the ball settles in **Pocket 6**, seventh from the left on an index-6 slot. Verifier output matches your game history line for line.

Frequently asked questions