Convert any number to scientific and engineering notation, and back again, with significant figures counted.
Scientific notation writes any number as one digit, a decimal part and a power of ten: 123456 becomes 1.23456×10⁵, and 0.000045 becomes 4.5×10⁻⁵. The exponent is simply how many places the decimal point travelled — positive when it moved to the left, negative when it moved to the right — and the rule that the leading part stays between 1 and 10 makes the form unique, so two numbers written this way can be compared at a glance. Engineering notation keeps the same value but forces the exponent to a multiple of three, so it lines up with the SI prefixes: the same 0.000045 is 45×10⁻⁶, forty-five micro-somethings.
The conversion here is done on the digits as text rather than on a floating-point value, so nothing is lost on the way in or out. The input is split into a sign, a run of digits and a decimal exponent; leading zeros are dropped, the exponent is worked out by counting positions, and the digits are then laid out again around a new decimal point. That is why a thirty-digit number keeps all thirty of its digits instead of collapsing into the nearest double. The same approach makes rounding to significant figures honest: the digit string is cut at the requested position and rounded with a carry, and when the carry overflows — 9.99 rounded to two figures — the exponent is bumped and the answer becomes 1.0×10¹ rather than the malformed 10×10⁰.
Significant figures are counted the way a lab report expects. Every digit from the first non-zero one onward counts, and trailing zeros in a whole number written without a decimal mark are flagged as ambiguous instead of being silently counted, because 1200 could mean two, three or four significant figures depending on how it was measured. Scientific notation exists precisely to remove that ambiguity: writing 1.2×10³ says two figures and nothing else. In practice this is the notation of physics, chemistry and astronomy — the Avogadro constant is 6.02×10²³ and the charge of an electron is 1.602×10⁻¹⁹ coulombs, and neither is readable written out in full. The tool runs entirely in your browser and never sends what you type anywhere.
Scientific notation writes a number as a × 10^b with 1 ≤ |a| < 10, where b is how many places the decimal point moved — positive to the left, negative to the right. Engineering notation expresses the same value with b forced to a multiple of 3, so that 1 ≤ |a| < 1000 and the exponent matches the SI prefixes (kilo, mega, giga, milli, micro, nano).
It is a way of writing any number as a value between 1 and 10 multiplied by a power of ten, such as 1.23456×10⁵ for 123456. It keeps very large and very small numbers readable and makes the number of significant figures explicit.
The exponent is always a multiple of three, so the mantissa can range from 1 up to 1000. That is what makes it line up with the SI prefixes: 45×10⁻⁶ reads directly as 45 micro-units, while the scientific form 4.5×10⁻⁵ does not.
Use e or a multiplication by a power of ten: 1.23e5, 1.23×10^5 and 1,23×10⁵ are all accepted. The tool converts it to the plain decimal form and normalises the mantissa for you.
Every digit from the first non-zero digit onward is counted, including zeros in the middle and zeros after a decimal mark. Trailing zeros in a whole number with no decimal mark are ambiguous, so they are reported as such instead of being counted.
No. The conversion is pure string arithmetic running in JavaScript on your device, with no requests to any server and nothing stored.
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