Camera Shutter Speed Converter (Fraction ↔ Decimal)
Convert camera shutter speeds between fraction form (1/250), decimal seconds (0.004 s), and time value in stops. Runs in your browser.
Enter a fraction (1/250), decimal seconds (0.004), or a bare denominator (250).
Photographers write shutter speed as a fraction of a second (1/250), while software and EXIF often use decimals (0.004 s). The time value Tv = log₂(1 ÷ seconds) expresses it in stops relative to one second — each whole stop halves or doubles the exposure time. 1/250 s ≈ 0.004 s ≈ Tv 7.97; one second is Tv 0; two seconds is Tv −1. Everything runs in your browser.
About this tool
Photographers and cameras express shutter speed as a fraction of a second — 1/250, 1/60, 1/1000 — because that is how the dial and viewfinder read, but software, EXIF metadata, scripts, and long-exposure work often need the value as a plain decimal in seconds. This converter translates freely between the two and adds the photographic 'stop' measure. You can type a shutter speed in any of the natural forms: a fraction like 1/250, a decimal like 0.004, or just the bare denominator 250 (interpreted as 1/250), and it returns the decimal seconds, the tidy fraction form, and the time value. The time value, Tv, is log₂(1 ÷ seconds): it expresses the shutter speed in stops relative to one second, which is how exposure actually scales. Each whole stop doubles or halves the exposure time, so the standard shutter sequence (1/1000, 1/500, 1/250, 1/125, 1/60…) steps by one stop each — every step lets in twice as much or half as much light. Knowing the decimal is handy for intervalometers and time-lapse intervals, for entering exposure times in editing or astrophotography software, for comparing speeds that aren't on the standard scale, and for any code that works in seconds. Knowing the Tv lets you reason about exposure trade-offs against aperture and ISO, which also move in stops. The tool handles the full range from very fast fractions (where it shows scientific notation for tiny decimals) through multi-second long exposures. Note that real cameras quantize to ⅓- or ½-stop increments and the marked '1/250' is nominally 1/256 in strict stop math, but the everyday fraction is what cameras display and what this tool uses. Everything runs in your browser; nothing is uploaded.
How to use it
- Type a shutter speed as a fraction (1/250), decimal seconds (0.004), or bare denominator (250).
- Or tap one of the standard-speed presets.
- Read the decimal seconds, the fraction form, and the time value (Tv) in stops.
- Copy whichever form you need for your camera, software, or code.
Frequently asked questions
- How do I convert 1/250 to decimal?
- 1 ÷ 250 = 0.004 seconds. Conversely, 0.004 seconds is 1/250. The tool does this both ways and also accepts a bare "250" as shorthand for 1/250.
- What is "time value" (Tv)?
- Tv = log₂(1 ÷ seconds), the shutter speed expressed in stops relative to one second. 1/250 s is about Tv 7.97; one second is Tv 0; two seconds is Tv −1. Each whole stop halves or doubles exposure time.
- Why do shutter speeds go 1/1000, 1/500, 1/250…?
- Each is one stop (a factor of two) from the next, so each step doubles or halves the light. This standard sequence lets photographers reason about exposure in even stops alongside aperture and ISO.
- Is 1/250 exactly a stop from 1/125?
- In everyday use yes — 1/125 to 1/250 is treated as one stop. Strictly, the marked values are rounded (a true one-stop step from 1/125 is 1/256), but cameras display the conventional fractions, which this tool uses.
- Can it handle long exposures?
- Yes. Enter values of one second or more (e.g. 2, 30) and it shows them as decimal seconds with the corresponding negative or zero Tv. Very fast speeds show tiny decimals in scientific notation.
- Is anything uploaded?
- No. The conversion runs entirely in your browser.