A calculator for engineers: engineering and scientific display, SI prefixes, physical constants, parallel resistors, decibels and number-base conversion.
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History
Use it as a stand-alone app
To install: use the browser menu, "Install app" or "Add to home screen". It then works offline.
Keyboard: digits and operators, Enter for the result, Esc to clear, Backspace to delete.
Formula
Engineering notation writes a value as a mantissa between 1 and 1000 times a power of ten whose exponent is a multiple of three:
x=m×103k,1≤∣m∣<1000,k∈Z
The exponent 3k maps to an SI prefix: 103 is kilo (k), 106 mega (M), 109 giga (G), 10−3 milli (m), 10−6 micro (µ), 10−9 nano (n) and 10−12 pico (p). Decibels use 20log10 for voltage ratios and 10log10 for power ratios, and parallel resistances combine as 1/∑(1/Ri).
Worked example
An RC low-pass filter uses R = 4.7 kΩ and C = 22 nF. Find its cut-off frequency.
Type 1 / (2 × pi × 4.7 k × 22 n) with the k and n prefix keys, and press =.
The resistance is 4700 Ω and the capacitance is 2.2×10⁻⁸ F, so the product is 1.034×10⁻⁴ s.
The answer is about 1539 Hz, shown as 1.539×10³ with the prefix 1.539 k.
For the power gained by doubling a voltage, dbv(2) gives 6.02 dB.
Common mistakes
Typing a prefix after a closing bracket. The prefix keys multiply the previous number, so use them directly after a value.
Confusing m (milli, 10⁻³) with M (mega, 10⁶). The keys are labelled with their case for exactly this reason.
Using dB(V) for a power ratio. Voltage ratios use 20 log, power ratios use 10 log.
Reading hex digits without the 0x prefix. Plain letters are treated as names, so write 0xFF, not FF.
Frequently asked questions
What is engineering notation?
It is scientific notation with the exponent forced to a multiple of three, so the number lines up with an SI prefix: 47 000 becomes 47×10³, which is 47 k. Press the display button until it shows ENG and the prefix appears under the result.
How do I enter 4.7 kΩ or 22 nF?
Type the number and then the prefix key: 4.7 then k gives 4.7×1e3, and 22 then n gives 22×1e-9. The prefix keys are on the SI prefixes tab. You can also type 4.7e3 or 22e-9 directly.
How do I add resistors in parallel?
Use the ‖ key (the par function): par(100, 220, 470) returns 60.0, the equivalent of three parallel resistors. For series, just add them.
Can it work in hexadecimal and binary?
Yes. Start a number with 0x, 0b or 0o for hex, binary or octal, for example 0xFF + 0b101. Whenever the answer is a whole number the panel below shows it in hex, decimal, octal and binary, with negatives as 64-bit two's complement. AND, OR, XOR, NOT, SHL and SHR are on the Bits and bases tab.
Where do the constants come from?
The speed of light, Planck and Boltzmann constants, Avogadro's number and the elementary charge use their exact SI 2019 values. Standard gravity is 9.80665 m/s². The vacuum permittivity, permeability and gas constant are CODATA 2018 values.