🧮 Math Calculators
Calculadora de porcentajes, IMC, edad y números romanos
Calcula porcentajes — calculadora de propina, calculadora de descuento, aumento de porcentaje y más.
Abrir herramienta →Calcula tu edad exacta desde cualquier fecha de nacimiento. ¿Cuántos años tengo hoy?
Abrir herramienta →Convierte números a números romanos y viceversa. Convertidor de números romanos gratuito.
Abrir herramienta →Calcula velocidad, distancia o tiempo a partir de los otros dos valores. Calculadora SDT gratuita.
Abrir herramienta →Suma, resta, multiplica y divide fracciones con soluciones paso a paso.
Abrir herramienta →Calcula tu promedio GPA a partir de calificaciones y créditos.
Abrir herramienta →Calcula la propina y divide la cuenta entre personas.
Abrir herramienta →Convierte números a palabras para cheques y facturas.
Abrir herramienta →Everyday arithmetic that is quicker to check than to do in your head — percentages, fractions, ratios of speed and distance, ages, tips, and numbers written out in words.
Each shows the working, which is the useful part. Percentage change in particular is a calculation most people can do and many get backwards, and seeing the expression makes the direction obvious.
Which tool do I want?
| If you… | Use |
|---|---|
| Percentage of, change between, or increase and decrease | Calculadora de porcentajes |
| You need to simplify or convert a fraction | Calculadora de fracciones |
| Two of speed, distance and time are known | Velocidad, distancia y tiempo |
| You need an exact age or a duration in years | Calculadora de edad |
| You are splitting a bill | Calculadora de propinas |
| You need a figure written out for a cheque or contract | Número a palabras |
| You are converting Roman numerals | Números romanos |
| You are working out a grade average | Calculadora de promedio GPA |
A 20% fall does not undo a 20% rise
Percentages are taken from whatever the current value is, so the base moves. Take 100, add 20% to get 120, then remove 20% — that 20% is now of 120, so you lose 24 and land on 96. To get back to 100 you would need 16.7%.
The same asymmetry runs through anything measured in percentages. An investment down 50% needs 100% to recover. A price cut by 30% needs a 43% increase to return to where it was.
Related, and worth keeping separate: percentage points versus percent. An interest rate moving from 2% to 3% has risen by one percentage point and by 50 percent. Both are correct, they describe the same change, and choosing whichever sounds more dramatic is a standard trick in reporting.