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How This Calculator Works
Rounding replaces a number with a simpler, nearby value — to a set number of decimal places, a
set number of significant figures, or the nearest multiple of another number. Enter a number and
pick which of the three you need.
Decimal places rounds everything after a certain position past the decimal point (e.g.
3.14159 to 2 decimal places is 3.14).
Significant figures keeps a set number of meaningful digits starting from the first non-zero
digit, regardless of where the decimal point falls (e.g. 123,456 to 3 significant figures is
123,000).
Nearest multiple rounds to the closest multiple of any number you choose — not just powers of
10 (e.g. rounding 47 to the nearest 5 gives 45… actually the nearest 10 gives 50).
The Formula
All three use the same core idea — divide by the target unit, round to the nearest whole number,
then multiply back:
Rounded Value=round(UnitNumber)×Unit
where “Unit” is 10⁻ᵈᵉᶜⁱᵐᵃˡ ᵖˡᵃᶜᵉˢ for decimal places, an order-of-magnitude-based unit for
significant figures, or simply the multiple you entered for nearest-multiple rounding.
Worked Example
Rounding 123,456 to 3 significant figures: 123,000. 2. Rounding 123,456 to 0
decimal places: 123,456 (already a whole number). 3. Rounding 123,456 to the nearest
1,000: 123,000. 4. Rounding 1.2345 to 2 decimal places: 1.23.
Cómo funciona esta calculadora
Redondear reemplaza un número con un valor cercano más simple — a una cantidad determinada de
decimales, una cantidad determinada de cifras significativas, o el múltiplo más cercano de otro
número. Ingresa un número y elige cuál de las tres opciones necesitas.
Decimales redondea todo después de cierta posición tras el punto decimal (por ejemplo,
3.14159 a 2 decimales es 3.14).
Cifras significativas conserva una cantidad determinada de dígitos significativos a partir
del primer dígito distinto de cero, sin importar dónde caiga el punto decimal (por ejemplo,
123,456 a 3 cifras significativas es 123,000).
Múltiplo más cercano redondea al múltiplo más próximo de cualquier número que elijas — no
solo potencias de 10 (por ejemplo, redondear 47 al múltiplo de 5 más cercano da 45… en
realidad, al múltiplo de 10 más cercano da 50).
La fórmula
Las tres usan la misma idea central — dividir entre la unidad objetivo, redondear al número entero
más cercano y luego multiplicar de nuevo:
Valor redondeado=redondear(UnidadNuˊmero)×Unidad
donde “Unidad” es 10⁻ᵈᵉᶜⁱᵐᵃˡ ᵖˡᵃᶜᵉˢ para decimales, una unidad basada en el orden de magnitud para
cifras significativas, o simplemente el múltiplo que ingresaste para el redondeo al múltiplo más
cercano.
Ejemplo resuelto
Redondeando 123,456 a 3 cifras significativas: 123,000. 2. Redondeando 123,456
a 0 decimales: 123,456 (ya es un número entero). 3. Redondeando 123,456 al múltiplo
más cercano de 1,000: 123,000. 4. Redondeando 1.2345 a 2 decimales: 1.23.
What is the difference between decimal places and significant figures?
Decimal places count digits after the decimal point specifically. Significant figures count meaningful digits starting from the first non-zero digit, regardless of where the decimal point falls — so 123,456 rounded to 3 significant figures is 123,000, not a number with only 3 digits after a decimal point.
How do I round to the nearest multiple of a number that is not a power of 10?
Use the "nearest multiple" option and enter whatever number you want to round to — 5, 25, 0.5, or any other value. The same divide-round-multiply approach works regardless of what the multiple is.
Why did rounding 1.005 to 2 decimal places not give exactly what I expected?
This is a well-known quirk of how computers store decimal numbers in binary floating point — a number like 1.005 isn't stored as exactly 1.005 internally, so rounding it can occasionally land on the value just below or above what you'd expect by hand. It affects virtually all calculators and spreadsheets that use standard floating-point math, not just this one.
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