Last updated: September 30, 2026 · By the FXPayback Research Desk
Quick answer: The rupiah broke Rp18,000 per dollar on September 29 because US 10-year yields hit a 19-year high above 5.2%, Brent oil is above $100 on US–Iran tensions, and investors are uneasy about Indonesia’s budget. Money is leaving emerging markets for dollar assets, and Bank Indonesia is intervening to slow the slide.
If you trade from Jakarta or Surabaya, you felt this one. The rupiah slipped through Rp18,000 per dollar on Tuesday for the first time since early August. Traders in Kuala Lumpur and Karachi are asking us the same thing: is this a one-day scare, or the start of something bigger?
Here’s what’s driving it, with the numbers.
What happened to the rupiah on September 29?
The rupiah weakened to Rp18,010 per dollar, its weakest level since August 4, according to The Star. The Jakarta stock market fell as much as 2.2% before trimming losses to 0.6%.
Zoom out and the trend is clear. Trading Economics shows USD/IDR around 17,946 late on Tuesday, with the rupiah down about 1.3% over the past month and 7.5% over the past year. The weakest level on record came in July 2026, near 18,279.
Why is the rupiah falling?
It’s not one thing. It’s three pressures landing at the same time:
- US yields at 19-year highs. The US 10-year Treasury yield pushed above 5.25%, the 2-year sits near 4.95% and the 30-year hit 5.58%, per Saxo. When a US bond pays over 5% with almost no risk, Indonesian bonds need to pay a lot more to keep foreign money.
- Oil above $100. Brent’s November contract traded above $107 on Tuesday as the US–Iran standoff around the Strait of Hormuz drags on. Indonesia imports much of its fuel, so expensive oil means more dollars leaving the country.
- Budget worries at home. The Jakarta Post points to capital outflows and fiscal risks on top of the global pressure. Investors have been nervous about heavy spending programmes and weaker tax collection, as The Southeast Asia Desk has noted.
One economist quoted by The Star, Fakhrul Fulvian, put it neatly: if bond yields are held below what private investors demand, “the adjustment can move into the currency instead.” In plain terms, when Bank Indonesia buys bonds to keep yields down, the pressure pops out in USD/IDR.
What is Bank Indonesia doing about it?
Bank Indonesia has kept its benchmark rate at 5.75% for three straight months after earlier hikes, and it is intervening across several markets to limit the fall, according to Trading Economics. A BI official told The Jakarta Post that the weakness reflects “continued concerns on global inflationary pressure.”
Be realistic about what intervention does. It slows a move and smooths out panic spikes. It rarely reverses a trend on its own while US yields keep climbing.
How does the rupiah compare with the ringgit and other currencies?
Not every Asian currency is getting hit the same way. Here’s the snapshot from Tuesday, September 29:
| Market | Level (Sep 29, 2026) | Source |
|---|---|---|
| USD/IDR | Rp18,010 (weakest since Aug 4) | The Star |
| USD/MYR | 4.0800/0865 at the open, slightly firmer ringgit | Malay Mail |
| US Dollar Index (DXY) | Above 101.20 | FXStreet |
| US 10-year yield | Above 5.25% | Saxo |
| Brent crude (Nov) | Above $107 | Saxo |
The ringgit is holding up better because Malaysia exports oil and gas, so high energy prices cut both ways there. Still, Bank Muamalat’s chief economist warned that higher US yields “could limit demand for emerging-market currencies, including the ringgit.” For traders in Karachi, the story rhymes: any oil-importing economy feels this squeeze.
What are the key USD/IDR levels and takeaways this week?
- Rp18,000: the psychological line. Expect Bank Indonesia to lean against moves above it.
- Around Rp18,279: the July record. A daily close above that puts the rupiah in fresh record-low territory.
- Rp17,880–17,900: the first support zone if the dollar cools. Trading Economics’ own end-of-quarter estimate sits near 17,882.
- Events: US PCE inflation on Wednesday and the September jobs report on Friday, per Yahoo Finance. Both land at 7:30 p.m. Jakarta time. Any US–Iran deal on Hormuz could knock oil lower and give the rupiah breathing room.
A candid word. Most retail brokers either don’t offer USD/IDR or quote it with wide spreads, so many Indonesian traders express this view through the dollar index, gold or USD/JPY instead. Whatever you trade, these are headline-driven markets. Size down, and work out your lot size with a position size calculator before you click buy.
How can Indonesian traders cut trading costs while the rupiah is weak?
Here’s the part nobody talks about. Your trading account is in dollars, but your life runs in rupiah. When the rupiah weakens, every dollar you pay in spread and commission costs you more at home. And volatile weeks like this one mean more trades, more stop-outs and more re-entries.
That’s the cost FXPayback gives back. Trade through your usual broker via FXPayback and we return up to 90% of the IB commission to you as cashback on every lot, win or lose.
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- 10 gold lots × $5 = $50
- Total: $100 back, roughly Rp1.8 million at today’s exchange rate
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Frequently Asked Questions
Why is the rupiah weak today?
US Treasury yields above 5.2%, oil prices over $100 from the US–Iran standoff, and worries about Indonesia’s budget are pulling money out of rupiah assets. The rupiah hit Rp18,010 per dollar on September 29, 2026.
What is the rupiah’s record low against the dollar?
According to Trading Economics, the weakest level on record was near Rp18,279 per dollar in July 2026.
Will Bank Indonesia raise interest rates again?
It’s possible but not certain. BI has held its rate at 5.75% for three months and is relying on market intervention for now. Another US rate hike or a spike in oil would raise the pressure to act.
How can Indonesian forex traders reduce their trading costs?
Trade smaller in volatile weeks, avoid entering right at news releases when spreads widen, and use a rebate service like FXPayback, which pays cashback on every lot you trade, win or lose, with withdrawals from $1.
Risk disclaimer: Trading forex, gold and CFDs involves significant risk and you can lose more than your deposit. This article is for information only and is not financial advice.