Hong Life CalculatorsUnderstanding the ETF premium and discount calculator — concept and principle
An exchange-traded fund has two prices: the market price at which its shares trade, and the net asset value (NAV), the value of the holdings per share. When the market price is above NAV the fund trades at a premium; below, at a discount. This calculator measures that gap, shows what you pay for 100 units of underlying value, and compares the fund's return with its index to give the tracking difference.
How it is calculated
- Premium / discount (%) = (market price ÷ NAV − 1) × 100; positive is a premium, negative a discount
- Paid per 100 of NAV = 100 × price ÷ NAV
- Tracking difference (percentage points) = ETF return − index return over the same period
Price and NAV must be per share and at the same moment; the returns must cover the same dates and both include or both exclude dividends.
The principle
ETF shares are created and redeemed in large blocks by authorised participants, usually large dealers. If the price rises above NAV, they can deliver the underlying securities, receive new ETF shares and sell them; if it falls below, they buy ETF shares and redeem them for the securities. This arbitrage normally keeps the gap small for funds with liquid holdings. Gaps widen when the holdings are hard to trade, when the underlying market is closed while the ETF trades, or in stressed markets. Tracking difference reflects the expense ratio, trading costs, cash drag, taxes on dividends and income from securities lending.
Worked example
- Market price 101.2, NAV 100.8; ETF return 9.4%, index return 9.9%.
- Premium = (101.2 ÷ 100.8 − 1) × 100 ≈ 0.397%.
- For 100 of NAV you pay 100 × 101.2 ÷ 100.8 ≈ $100.40.
- Tracking difference = 9.4 − 9.9 = −0.5 percentage points.
How to read the result
For large funds tracking liquid stock indices, the gap is usually a small fraction of a percent. A persistent premium means buyers pay extra that they may lose if the gap closes; a discount can work in your favour when buying. A tracking difference close to minus the expense ratio is normal; far worse suggests extra costs. Tracking error, the volatility of the difference over time, measures consistency and needs a series of returns.
Common mistakes
- Comparing a live price with the previous day's official NAV, especially for foreign holdings.
- Mixing a price-return index with a fund's total return.
- Treating tracking difference and tracking error as the same thing.
Frequently asked questions
Is buying at a premium always bad?
Not if you sell at a similar premium; the risk is that it shrinks or turns into a discount while you hold.
Where can I find the NAV?
Fund issuers publish the daily NAV, and many exchanges show an indicative value during trading hours.
Why is the tracking difference negative?
Fees and costs are taken from the fund but not from the index.
Sources: U.S. SEC, Investor.gov, "Exchange-Traded Funds (ETFs)" investor bulletin · Investment Company Institute, Investment Company Fact Book (ETF creation and redemption)