Check the reference behind the percentage
The large percentage shows how far the displayed value is from its reference: subtract the reference, divide by it and multiply by 100. A reference of 100 and a value of 101 produce a 1% gain. The formula is shared, but the reference is not. A stock's prior trading close, a currency's 24-hour comparison and an after-hours instrument's related cash close should not all be read as yesterday at the same time.
The baseline marks that reference on the chart. Read the line's position alongside the sign so changing the color palette does not change your interpretation. Percentage guide lines mark relative distances from the reference. The vertical scale adapts to the data, however: equally tall moves on different charts need not be equal changes. Compare percentages and units, not just the height of the line.
Regular equities generally compare with the prior trading close
Regular stocks, ETFs and equity indexes generally use the previous trading session's close. On Monday this is usually Friday, but holidays can push it further back. A prior calendar day and a prior trading session are different things. After a session ends, its displayed closing change still uses the earlier session's reference. Corporate actions such as stock splits also require care when comparing prices.
Check the unit below the chart: the Nikkei uses yen, other indexes may use points, and U.S. stocks and ETFs use USD. The absolute change is a difference in that unit; the percentage is a proportion. Use the percentage to compare direction and magnitude before inspecting an absolute price difference.
Regular FX uses a moving 24-hour comparison
Regular FX charts normally display the latest 24 hours and use an available observation near that boundary as the reference. The boundary moves with time, so the percentage can change even if the current price is nearly unchanged. The observation dropping into the comparison position has changed. An exact trade at the same second is not always available, and incomplete history may require an available reference value.
During the weekend closure, the last regular-session chart is retained. At reopening, new points follow Friday's line and the closed interval is compressed out of the horizontal axis. This creates a trading-time view around the weekend. It does not change the comparison policy into a prior-session-close policy. Keep the horizontal presentation separate from the percentage calculation.
After-hours charts and yields need extra care
After-hours instruments with a related cash reference generally use the prior trading close while the regular market is open and the latest close while it is closed. A reference update after the close can therefore change the displayed percentage. When regular FX is closed, Sunday USD/JPY uses the latest regular USD/JPY closing value. That is not the same reference as regular FX's rolling 24-hour comparison.
Crypto and commodities can use rolling windows or instrument-specific references, so one category does not guarantee identical calculations. For yields, a change from 1.00% to 1.10% is 0.10 percentage points but a 10% relative increase. Read both the unit and reference, and check status when history is missing or delayed. An unavailable reference should not be interpreted as a zero change.
Display behavior checked on October 4, 2026. Examples are illustrative, not investment advice. See the disclaimer.