Type any number — large, small or already in E-notation — to convert it to scientific, engineering and decimal forms, count its significant figures and round it to as many as you need.
Scientific
1.2345 × 10^4
Significant figures
5
Calculator
Scientific notation
1.2345 × 10^4
12345 has 5 significant figures.
Engineering
12.345 × 10^3
Significant figures
5
Rounded to 3 sig figs
12,300
Scientific
1.2345 × 10^4
Engineering
12.345 × 10^3
E-notation
1.2345e4
Decimal
12,345
Magnitude
Scientific notation and significant figures
Scientific notation writes a number as a mantissa between 1 and 10 times a power of ten, which makes very large or very small numbers compact and comparable. Engineering notation is the same idea but restricts the exponent to multiples of three, lining up with units like kilo, mega and milli.
Significant figures are the digits that carry real precision. All non-zero digits count, zeros between them count, leading zeros never count, and trailing zeros count only when a decimal point is present. Rounding to a chosen number of significant figures keeps the most meaningful digits and drops the rest.
What is the difference between scientific and engineering notation?
Both use a mantissa times a power of ten. Scientific notation keeps the mantissa between 1 and 10; engineering notation forces the exponent to a multiple of three so it maps onto metric prefixes, so 12,345 is 1.2345×10⁴ scientifically but 12.345×10³ in engineering form.
Why are trailing zeros sometimes significant?
A trailing zero after a decimal point shows measured precision, so 1.50 has three significant figures. A trailing zero in a bare integer like 1500 is ambiguous and is treated as not significant unless a decimal point is written.
How does rounding to significant figures work?
It keeps the requested number of meaningful digits starting from the first non-zero digit, then rounds the rest. For example 1234 to 2 significant figures is 1200, and 0.004567 to 2 is 0.0046.
Results are estimates. Verify with a professional for important decisions.
About this calculator
This calculator converts any number to scientific, E and engineering notation, counts its significant figures, and rounds to a chosen number of sig figs. Use it to check your working in science or maths class, prepare values for lab reports, or simply understand the scale of very large or very small numbers.
How to read your results
The headline result shows your number in standard scientific notation — mantissa × 10^exponent — with the same value also displayed in engineering notation (exponent a multiple of 3) and compact E-notation. The stats row beneath lists the number of significant figures the calculator detected and the value rounded to your chosen sig-fig count. The magnitude number line at the bottom marks where your number sits on a scale from 10^−15 to 10^15.
Worked example
Enter 12345 as the number and 3 as the significant-figures target.
The calculator returns scientific notation 1.2345 × 10^4, engineering notation 12.345 × 10^3, E-notation 1.2345e4, detects 5 significant figures in the input, and rounds to 3 sig figs giving 12300.
Frequently asked questions
What is scientific notation and why is it useful?
Scientific notation expresses a number as a mantissa between 1 and 10 multiplied by a power of ten (for example 6.02 × 10^23). It makes arithmetic on very large or very small numbers manageable, removes ambiguity about trailing zeros, and is the standard format in science, engineering and computing.
What is the difference between scientific and engineering notation?
In scientific notation the exponent can be any integer and the mantissa is always between 1 and 10. In engineering notation the exponent is always a multiple of 3, so the mantissa ranges between 1 and 1000. Engineering notation aligns with SI prefixes such as kilo (10^3), mega (10^6) and micro (10^−6), making it easier to read units.
How do I count significant figures correctly?
All non-zero digits are significant. Zeros between non-zero digits are always significant. Leading zeros (before the first non-zero digit) are never significant. Trailing zeros in a whole number without a decimal point are ambiguous and treated as non-significant; a trailing decimal point (writing "1500." instead of "1500") signals that those zeros are significant. In scientific notation every digit of the mantissa is significant.
How it's calculated
To convert to scientific notation the calculator finds the exponent as floor(log₁₀|x|) and divides x by 10^exponent to get the mantissa. Engineering notation uses the same approach but rounds the exponent down to the nearest multiple of 3. Significant-figure counting applies the standard rules: the algorithm strips the sign, identifies the first non-zero digit as the start of the significant range, and for bare integers without a decimal point drops trailing zeros before counting. Rounding to n sig figs is done by computing the scale factor 10^(n − ceil(log₁₀|x|)), multiplying, rounding to the nearest integer, and dividing back.
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