Scientific Notation Converter
Convert numbers between decimal and scientific (E) notation, including very large and very small values.
How to use
Enter a complete decimal or E-notation value. Leave significant digits blank to preserve every digit and trailing zero, or choose a precision and rounding rule. Engineering exponents are always multiples of three.
Convert any decimal to scientific and engineering notation — or paste E notation like 1.5e6 and get the plain decimal back. Type 12345.678 and read 1.2345678e+4 (scientific, i.e. 1.2345678 × 10⁴) and 12.345678e+3 (engineering) instantly, with an exact digit-by-digit engine underneath.
The engine is string-and-BigInt based, not floating point: every digit you type is preserved, including trailing zeros (1.500 stays 1.500, because in measurement those zeros carry precision). Leave “Significant digits” blank to keep everything, or set a precision and pick one of four rounding rules: half up, half even (banker’s rounding), toward zero, away from zero.
Engineering notation keeps the exponent a multiple of 3 so it maps onto SI prefixes: 12.345678e+3 reads directly as ≈12.35 k. That is why engineers prefer it — 4.7 × 10⁻⁶ F is harder to say than 4.7 µF.
Boundaries: incomplete E notation such as “1e” is rejected outright rather than half-parsed. Rounding rules only differ on ties — 2.5 to one significant digit is 3 under half-up but 2 under half-even, which is exactly why banks and IEEE 754 default to half-even: it does not drift upward over many roundings.
Published test vectors — each validated against the live tool: 12345.678 → 1.2345678e+4 (= 1.2345678 × 10⁴) · engineering form 12.345678e+3 · 6.02e23 (Avogadro) parses and round-trips · 9.109e-31 (electron mass) keeps all four digits · trailing zeros preserved when significant digits is blank. Last verified: 2026-08-12.
FAQ
What is the difference between scientific and engineering notation?
Scientific notation normalizes the coefficient to 1–10 (1.2345678e+4). Engineering notation forces the exponent to a multiple of 3 with a coefficient from 1 up to 1000 (12.345678e+3), so it maps directly to SI prefixes like k, M, µ, n.
Why does 1.500 keep its trailing zeros?
Because this converter uses an exact string/BigInt engine, not floating point. In measurement, 1.500 means known-to-three-decimals; collapsing it to 1.5 silently destroys precision information. Set significant digits explicitly if you want fewer digits.
What is half-even (banker’s) rounding and when should I use it?
On exact ties it rounds to the nearest even digit: 2.5 → 2 but 3.5 → 4. Over many roundings this avoids the upward bias of always rounding halves up, which is why finance and IEEE 754 floating point default to it.
How do I type very small numbers?
Use E notation with a negative exponent: 9.109e-31 for the electron rest mass, 3e-9 for 3 nanoseconds. The converter shows the full decimal expansion and both notations.
Why was my input “1e” rejected?
It is incomplete — there is no exponent after the E. The parser rejects partial forms instead of guessing, so you never get a silently wrong conversion from a typo.
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