Precision

Understanding token decimals, price formats, and amount conversions is critical for correct trading.

Token Decimal System

Both USDT (collateral) and outcome tokens (YES/NO) use 18 decimal places:

Human Amount	Wei Amount
1 USDT	1,000,000,000,000,000,000 (10^18)
0.5 USDT	500,000,000,000,000,000
100 USDT	100,000,000,000,000,000,000

Price Format

Prices are strings representing implied probability:

• Valid range: 0.01 to 0.99

• Maximum 4 decimal places

• "0.50" = 50% probability = $0.50 per token = $1.00 payout if correct

Wei Conversion

The SDK provides a safeAmountToWei utility for converting human-readable amounts to wei:

example.ts

import { safeAmountToWei } from '@opinion-labs/opinion-clob-sdk';

// Convert human amount to wei
const weiAmount = safeAmountToWei(100.0, 18); // 100 USDT -> wei
console.log(weiAmount); // 100000000000000000000n (BigInt)

// For smart contract operations, pass BigInt directly
await client.split(123, weiAmount);

Use BigInt for wei amounts to avoid JavaScript number precision issues.

Example comparisons:

bigint-examples.ts

// Correct - BigInt
const amount = BigInt(100) * BigInt(10 ** 18);

// Avoid - Number (loses precision for large values)
const amount = 100 * 10 ** 18; // May lose precision!

You can also construct wei values directly with BigInt:

direct-wei.ts

// 100 USDT in wei
const oneHundredUsdt = BigInt(100) * BigInt(10 ** 18);

// 0.5 USDT in wei
const halfUsdt = BigInt(5) * BigInt(10 ** 17);

Order Amount Handling

When placing orders, provide amounts in human-readable format (not wei). The SDK handles conversion internally.

place-order.ts

import { OrderSide, OrderType, type PlaceOrderDataInput } from '@opinion-labs/opinion-clob-sdk';

// Spend 10 USDT - provide as string, SDK converts to wei internally
const order: PlaceOrderDataInput = {
  marketId: 123,
  tokenId: 'token_id',
  side: OrderSide.BUY,
  orderType: OrderType.LIMIT_ORDER,
  price: '0.5',
  makerAmountInQuoteToken: '10', // 10 USDT (human-readable)
};

The distinction is important:

• Order amounts (makerAmountInQuoteToken, makerAmountInBaseToken): human-readable strings, SDK converts internally

• Smart contract amounts (split, merge): wei as bigint, you must convert manually

Common Errors to Avoid

1

Wrong decimals

USDT uses 18 decimals (not 6) in this system.

2

Float arithmetic

Use BigInt for precise wei calculations.

3

Price range

Prices must be within [0.01, 0.99].

4

Manual wei conversion for orders

The SDK handles this; provide human-readable amounts.

5

Manual wei conversion for split/merge

You must provide wei amounts directly.