---
title: "Which AI Chat Can Calculate IDX Position Size from a Rupiah Risk Budget?"
description: "A real chat test sizes a hypothetical position at 31 lots after fees, rejects the 32nd lot and shows why a worse exit can exceed the planned loss budget."
author: "Trade Inc Research"
published_at: "2026-10-06T07:10:21Z"
updated_at: "2026-10-06T07:10:24Z"
canonical: "https://tradeinc.app/en/blog/ai-chat-idx-position-size-risk-budget"
tickers: []
citations: ["https://www.idx.id/en/products-services/trading-hours-and-mechanism/","https://www.investor.gov/introduction-investing/general-resources/news-alerts/alerts-bulletins/investor-bulletins-14"]
---

# Which AI Chat Can Calculate IDX Position Size from a Rupiah Risk Budget?

A real chat test sizes a hypothetical position at 31 lots after fees, rejects the 32nd lot and shows why a worse exit can exceed the planned loss budget.

## Summary

Trade Inc chat can help turn a stated cash limit and planned-loss budget into a checkable whole-lot position-size calculation. In our authenticated Pro demo, it returned **31 lots**, included assumed buy and sell fees, and explained why 32 lots would exceed the loss budget even though sufficient cash remained.

The more important result was the stress test: changing only the exit price increased the calculated loss from **Rp494,837.50 to Rp804,062.50**. A budget based on a planned exit is not a guarantee that a real loss will stay below that budget.

## Key takeaways

- Supply both available cash and a planned-loss budget; they constrain different things.
- Include transaction costs before rounding down to whole lots.
- Ask the chat to test one extra lot, not merely produce a plausible number.
- Keep the position size unchanged when testing a worse exit.
- This is a hypothetical calculation, not a ticker recommendation, backtest or executed order.

## 1. Give chat a complete, bounded scenario

We opened a new conversation, kept the **Cepat** response mode, entered the scenario below and pressed **Kirim**. The walkthrough was tested on 6 October 2026 in an authorized Pro demo account. It does not establish access on every plan.

| Input | Illustrative assumption |
|---|---:|
| Entry price per share | Rp2,500 |
| Planned exit price per share | Rp2,350 |
| Available cash | Rp10,000,000 |
| Planned-loss budget | Rp500,000 |
| Shares per lot | 100 |
| Buy fee | 0.15% |
| Sell fee | 0.25% |
| Worse exit for stress test | Rp2,250 |

The fees are assumed all-in rates, not a quote from a broker. No market data was requested, and no real company was assigned these prices. IDX states that regular- and cash-market shares trade in lots of 100 shares; negotiated-market transactions are different. [IDX trading mechanism](https://www.idx.id/en/products-services/trading-hours-and-mechanism/).

A reusable request is: “Calculate maximum whole lots under both my cash limit and planned-loss budget, including the stated fees. Show the formula, cash used, cash left and why one extra lot fails. Keep the size fixed and test a worse exit. Do not place orders or save a portfolio.”

![Actual Trade Inc chat showing the hypothetical inputs, 31-lot answer and fee-adjusted calculation](https://cdn.sanity.io/images/eybaj6wm/production/c4fac959193a2eaf9381e87bee974a6639d591f8-1440x900.png)

*The submitted prompt and actual response. The interface labels are Indonesian; we requested the calculation in English. These are scenario inputs, not observed market prices.*

## 2. Check which constraint actually binds

For a long position, compare the fee-inclusive entry cost with net exit proceeds:

`planned loss per share = entry × (1 + buy fee) − planned exit × (1 − sell fee)`

Here that is **Rp2,503.75 − Rp2,344.125 = Rp159.625 per share**. Each 100-share lot therefore costs Rp250,375 to enter and has Rp15,962.50 of planned loss under these assumptions.

Cash supports 39 whole lots, but the loss budget supports only 31. Choose the smaller number—not the average and not whichever permits the larger trade.

| Check | 31 lots | 32 lots |
|---|---:|---:|
| Shares | 3,100 | 3,200 |
| Entry cash including buy fee | Rp7,761,625 | Rp8,012,000 |
| Loss at planned exit including fees | Rp494,837.50 | Rp510,800 |
| Within Rp500,000 loss budget? | Yes | No |

The chat also returned **Rp2,238,375 cash left** for 31 lots. We independently recalculated these values using decimal arithmetic, including the failed 32-lot boundary. All matched the response.

This boundary check is useful when reviewing AI output: a feasible answer is not necessarily the maximum feasible answer. Here 31 passes and 32 fails the binding constraint.

## 3. Stress the exit, not the answer

Keeping 3,100 shares fixed, an exit at Rp2,250 gives net proceeds of Rp2,244.375 per share. The resulting loss is **Rp804,062.50**—Rp304,062.50 above the original budget.

![Trade Inc chat showing the sizing table, worse-exit loss and the beginning of its supplied calculation code](https://cdn.sanity.io/images/eybaj6wm/production/9ecd98c7e0a09625d95ea009f9b6f55c1d8e84ab-1440x900.png)

*The actual result and supplied code. Our editorial check independently reproduced the numbers; the displayed code is not a guarantee that every future response will be correct.*

Do not resize the position downward in this stress test. That would answer how many shares you might choose before buying under a different assumption, not what happens to the position already being tested.

The SEC’s investor bulletin explains that a stop trigger does not guarantee the execution price, while a stop-limit may fail to execute. This is cited for the general execution-risk distinction, not as evidence that a particular order type is available at every Indonesian broker. Check your broker’s actual facilities and terms. [Investor.gov order-type bulletin](https://www.investor.gov/introduction-investing/general-resources/news-alerts/alerts-bulletins/investor-bulletins-14).

## What this demonstration does—and does not—prove

The demonstrated capability is conversational scenario calculation with formulas, numerical results and supplied code. It is not an automatic risk-control system, broker order placement, a live portfolio update or a test of historical returns.

The calculation assumes one entry price, one exit price, proportional fees and no extra minimum charge. It omits partial fills, additional taxes or charges outside the assumed rates, liquidity constraints and any inability to exit. Replace assumptions with your actual costs before using the arithmetic.

Reject or revise the output if its cash usage exceeds available cash, the next-lot test is missing, fee units are confused, or the stress case silently changes the position size. This worked example verifies one response, not universal reliability.

## Who needs this workflow?

It suits someone who wants to change assumptions conversationally and inspect why the result changes. A spreadsheet or calculator may be enough for a single fixed scenario; this test does not establish that Trade Inc is uniquely capable or better than alternatives.

For account-weight changes rather than a loss-budget constraint, see [the purchase-preview guide](/en/blog/preview-stock-purchase-cash-portfolio-weight). For broader hypothetical modeling, see [custom portfolio simulations in chat](/en/blog/ai-chat-portfolio-simulations).

## Conclusion: verify the boundary and the failure case

A useful answer gives more than a lot count. It identifies the binding limit, proves that the next lot fails, and shows what happens if execution is worse than planned.

In this illustration, 31 lots meets the stated assumptions; it is not a recommendation to buy 31 lots of any stock. The Rp804,062.50 stress loss is precisely why the planned budget must not be described as a guaranteed maximum.

*Publisher disclosure: Trade Inc publishes this guide about its own product. Screenshots are from an authorized product demonstration. Figures are hypothetical and are not investment advice.*


[1]: https://www.idx.id/en/products-services/trading-hours-and-mechanism/ "IDX — Trading Hours and Mechanism"
[2]: https://www.investor.gov/introduction-investing/general-resources/news-alerts/alerts-bulletins/investor-bulletins-14 "Investor.gov — Understanding Order Types"