Convert 0.00042
4.2 × 10^−4
With two significant figures, the coefficient is 4.2 and the exponent is −4. Moving the decimal four places to the right gives the coefficient; the negative exponent restores the original small value.
Numbers
Scientific Notation Calculator
Make very large and very small numbers easier to read. Convert one number or calculate with two, then compare three equivalent display forms.
Convert or calculate scientific numbers
Scientific notation
Enter a number, then select Calculate.
Calculations stay in your browser. Successful results appear in your tab's recent calculations.
Three useful examples
Add 3.2e5 and 4.5e4
3.65 × 10^5
Rewrite 4.5 × 10^4 as 0.45 × 10^5. Then add 3.2 + 0.45 to get 3.65. The exact decimal total is 365,000.
Divide 1e3 by 3
≈ 3.33333 × 10^2
At six significant figures, 1,000 ÷ 3 is displayed as 333.333. The repeating digits are rounded only for display; changing the precision uses the original exact fraction.
Notation, arithmetic, and rounding
Normalized scientific notation writes a nonzero number as a × 10n, with 1 ≤ |a| < 10 and an integer exponent n. Positive exponents make powers of ten larger; negative exponents represent reciprocals. The letter e is a compact input format: 6.02e23 means 6.02 × 1023, not the mathematical constant e.
For multiplication, multiply the coefficients and add the exponents: (a × 10m)(b × 10n) = ab × 10m+n. For division, divide the coefficients and subtract the exponents, with b ≠ 0. For addition or subtraction, first express both numbers using the same exponent, then combine the coefficients. Normalize the result afterward.
Choose 1–20 significant figures. This tool rounds to the nearest value, with exact ties away from zero: at three figures, 1.235 becomes 1.24 and −1.235 becomes −1.24. A carry can change the exponent: 9.99 at two figures becomes 1.0 × 101. The coefficient retains trailing zeros to show your chosen display length.
Arithmetic uses exact integer fractions of the entered decimal values. No intermediate decimal rounding is used, including for cancellation or division. Only the final display is rounded. The ≈ marker is based on an exact comparison, and the full decimal field expands the displayed result rather than implying extra precision.
Each input accepts up to 100 digits in its mantissa, counting zeros, and an optional integer e exponent from −100 through 100; the total input limit is 128 characters. Leading + or −, .5, 5., and uppercase E are accepted. Commas, embedded spaces, ×10 notation, fractions, and multi-step expressions are not accepted. A result's exponent may fall outside the input range after calculation.
Zero is shown with exponent 0, such as 0.00000 × 100 at six figures. Negative zero is displayed as zero. These zeros and any extra trailing zeros are formatting choices; this tool does not infer measurement uncertainty or apply laboratory significant-figure propagation rules.
Reference: OpenStax — Integer Exponents and Scientific Notation. See the calculation policy for the site's general approach to precision.
Common questions
Does a negative exponent mean a negative number?
No. 2e-3 is positive 0.002. A minus sign before the coefficient makes it negative: -2e-3 is −0.002.
Why do I see more zeros than I typed?
The coefficient is padded to your selected number of significant figures. For example, 1.2 becomes 1.20000 × 10^0 at six figures. Its numeric value is unchanged; the display does not claim a more accurate measurement.
Is the full decimal exact when the result has ≈?
It is the full decimal expansion of the rounded value shown above it. It is not the unrounded answer. Increase the number of displayed figures to see more digits of the original result, up to 20.
Can I enter an entire expression such as 2e3 + 5e2?
Choose Add, enter 2e3 in the first field and 5e2 in the second. Each field accepts one number. For ordinary arithmetic expressions, use the Standard Calculator.