Education Probability

Weighted Random Selection Explained: How Crypto Lottery Probability Works

Published April 2026 · 9 min read · By Decentralotto Team

If you‟ve ever wondered exactly how your chances of winning are calculated in a crypto lottery, this guide is for you. Decentralotto uses a weighted random selection algorithm — a straightforward, mathematically transparent system that ties your winning probability directly to your stake. No black box, no hidden formula.

The Core Concept: Your Stake = Your Probability

In a weighted random lottery, your probability of winning equals your stake divided by the total pool. It‟s proportional selection — the more you invest, the higher your chances. But crucially, even the smallest ticket has a real, mathematically defined chance of winning.

P(win) = Your Stake ÷ Total Pool × 100%

Example: if the total pool is $1,000 and you deposit $100, your winning probability is exactly 10%. Not approximately — exactly.

How the Algorithm Works Step-by-Step

Step 1: Build the Ticket Line

When players join a lottery round, each player is assigned a consecutive range of numbers proportional to their stake. Imagine a number line from 0 to the total pool value. Each player «owns» a segment of that line.

Round Pool: 1,000 USDT Player A: 400 USDT → owns range [0, 400] Player B: 300 USDT → owns range [400, 700] Player C: 200 USDT → owns range [700, 900] Player D: 100 USDT → owns range [900, 1000]

Step 2: Generate a Random Number

When the draw condition is met (timer expires, pool target reached, or player count reached), the system generates a single random number between 0 and the total pool value (0–1000 in this example).

Step 3: Find the Owner of That Range

Whichever player‟s range contains the random number wins the round.

Random Number Generated: 647 → 647 falls in range [400, 700] → Player B WINS

Step 4: Calculate the Prize

The winner receives their own stake back (always), plus 90% of all other players‟ stakes. The platform retains 10% of others‟ stakes as its fee — and 0% of the winner‟s own stake.

Player B wins with $300 stake in a $1,000 pool: Others' stakes: $400 (A) + $200 (C) + $100 (D) = $700 90% of others' stakes: $630 Player B's prize: $300 (own) + $630 = $930 USDT Platform fee: 10% × $700 = $70 USDT (Fee is on OTHERS' stakes only — never on winner's own money)

Visual Example: Winning Probabilities

Four players, $1,000 total pool. Here‟s how their probability splits:

Player A
$400
40%
Player B
$300
30%
Player C
$200
20%
Player D
$100
10%

Why Weighted Selection Is Fairer Than Equal-Chance Lotteries

Traditional lotteries often give every ticket buyer the same odds regardless of how much they spent. In some formats, this is fair. But in a prize-pool format where one player puts in $500 and another puts in $5, giving them equal odds is actually unfair to the larger depositor.

Weighted selection aligns risk and reward mathematically. The player who deposits 10× more has 10× the probability — they take proportionally higher risk and get proportionally higher odds. This is the same principle as any rational investment or insurance system.

Weighted selection doesn‟t favor the house — it simply reflects reality: bigger stake = bigger skin in the game = bigger proportional chance of winning.

Can a Small Ticket Win Against a Whale?

Yes — and this is the exciting part. A player with $10 in a $1,000 pool has a 1% chance of winning. That‟s a low probability, but it‟s a real one. If they win, they receive $10 (own stake back) + 90% × $990 (others‟ stakes) = $10 + $891 = $901 USDT.

A $10 investment turning into $901. That‟s an 89× return. Their probability was only 1%, but the payout reflects the asymmetric upside that makes lottery formats exciting. The math is honest: low probability, high upside — which is exactly what players opt into voluntarily.

How Decentralotto‟s Fee Structure Works with Weighted Selection

The fee structure interacts with weighted selection in an important way: you can never walk away with less than what you deposited if you win. Here‟s why:

This means there‟s no «winning but still losing» scenario. If you win, you profit. The platform‟s revenue comes entirely from a portion of the prize pool generated by non-winners‟ contributions.

Weighted Selection Across Different Lottery Types

Speed Round and Jackpot

Both use standard weighted selection — your stake vs. total pool. More players and larger deposits move your probability proportionally. These formats have no fixed probability; it depends entirely on who else plays.

Infinity Pool

Same weighted selection, but the pool grows until exactly 100 players join. Because everyone knows the draw triggers at 100 players, pools can grow large before triggering — making single-draw prizes potentially very high.

Stack 50

Fixed prize of 500 USDT. Weighted selection still applies between the 50 players, but the total payout is predictable. Your probability = your stake / total deposited by all 50 players.

War of Attrition

The exception: War of Attrition does NOT use weighted selection. The last player to buy a ticket before the countdown expires wins — this is a timing and strategy format, not a probability format.

Why This Model Is Transparent

The beauty of weighted random selection is that it‟s auditable. The algorithm is simple enough to describe in a paragraph. Given the list of player stakes and the random number, anyone can manually verify whether the correct player was identified as the winner. There‟s no complex formula to hide manipulation in.

Combined with on-chain USDT payouts verifiable on Arbiscan and Tronscan, this gives players maximum possible confidence in draw outcomes. Read the full algorithm documentation on our Provably Fair page.

Summary

Ready to play? Register free, deposit USDT on Arbitrum or TRON (min 5 USDT), and join an active lottery round. Every ticket has a provably fair chance.

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