Epoch Seconds to Milliseconds Converter
Convert Unix timestamps between 10-digit seconds and 13-digit milliseconds with exact integer output. This is useful when you move timestamp values between backend APIs, SQL functions, browser events, and JavaScript runtimes that use different units.
Seconds to Milliseconds
Milliseconds to Seconds
Why this conversion matters in production
Seconds and milliseconds are both valid Unix time units, but mixing them causes subtle bugs. A 13-digit value passed to a system expecting 10-digit seconds often looks thousands of years in the future. A 10-digit value interpreted as milliseconds looks like a date near 1970. Converting units explicitly prevents cache expiration bugs, bad analytics windows, and failed API signature checks that depend on accurate timestamp boundaries.
Quick rule of thumb
Use digit length as the first check. Most current epoch values in seconds are around 10 digits. Milliseconds are around 13 digits. For conversions, multiply seconds by 1,000 to get milliseconds, and divide milliseconds by 1,000 to get seconds. For database filters and most REST APIs, seconds are common. For frontend events and JavaScript Date APIs, milliseconds are usually required.
Related timestamp tools
Use this page for unit conversion, then switch to date conversion when you need human-readable output. You can also copy a live current value from the current timestamp pages and test your API request payloads immediately.