Tools

Every tool on this site lives next to the topic page that introduces the concept it relates to — calculators, designers, decoders and interactive visualisers. Use the search box to filter, then click any card to open the tool in context.

These tools started off as a separate web app called NinjaCalc in 2015. They were ported across and embedded in this blog in 2026, at which point NinjaCalc was sunset.

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Battery lifetime estimator

Estimate how long a battery lasts from its capacity, a duty-cycled load, protection-circuit (PCM) current and self-discharge. Simulated month-by-month, with temperature, usable-capacity and ageing adjustments.

BLE advertising packet decoder/builder

Paste a raw BLE advertising payload as hex to see its AD structures broken out, or build a payload from the structure editor and watch the hex update in real time.

Boost converter

Generic boost-converter design helper (CCM): from V_in, V_out, diode/switch drops, switching frequency, output current and ripple, compute the duty cycle, average and peak inductor current, and required inductance.

Buck converter

Generic buck-converter design helper: from V_in, V_out, diode/switch drops, switching frequency, output current and ripple, compute the duty cycle and required inductance.

Camera lens field-of-view calculator

Calculate the angular field of view, scene coverage and on-target spatial resolution (mm/pixel) for a camera sensor and lens, or solve in reverse for the focal length needed to cover a required scene width. Includes presets for popular embedded sensors (IMX477, IMX296, OV5647, and more).

Capacitor charge (Q = CV)

Solve for any one of charge, capacitance or voltage in the fundamental capacitor equation Q = CV, given the other two.

Capacitor energy (E = ½CV²)

Solve for any one of energy, capacitance or voltage in the capacitor energy equation E = ½CV², given the other two.

Capacitor impedance & reactance

Compute a capacitor's reactance Xc = 1/(2πfC) and its full impedance magnitude |Z| including ESR and ESL, plus the self-resonant frequency. Plots |Z| vs frequency showing the capacitive, resonant and inductive regions.

COBS encoder/decoder

Encode raw bytes into a Consistent Overhead Byte Stuffing (COBS) frame, or decode a COBS frame back into the original data. Enter bytes as hex; the tool validates the input and appends/strips the 0x00 packet delimiter.

CRC calculator

Compute the CRC of arbitrary data (text or hex) against any of 40 pre-defined CRC algorithms — from CRC-3/ROHC through CRC-64. Shows the algorithm parameters so you can verify what you're actually computing.

Current-source resistor (JFET / depletion MOSFET)

Calculate the source resistor R_S for a JFET or depletion-mode MOSFET wired as a two-terminal constant-current source, from I_DSS, V_GS(off) and the desired current.

Dew point (Magnus)

Solve the August-Roche-Magnus equation for air temperature, relative humidity or dew point given the other two. Useful when working with humidity sensors that report temperature and RH.

E-series resistor finder

Find the closest E6 / E12 / E24 / E48 / E96 / E192 preferred value to a desired resistance, with percentage error and closest equal-or-higher / equal-or-lower values for each series.

EIRP compliance world map

Enter your transmitter power, antenna gain and band; a world map colours each country green or red based on whether your EIRP is within that jurisdiction's regulatory limit.

Exponential moving average (EMA) filter explorer

Interactive EMA filter explorer. Drag α to see how it smooths step, sine, square and noisy signals in the time domain, then switch to the Bode tab to watch the magnitude/phase response and -3 dB cut-off change.

Fixed-point (Q-format) explorer

Convert real numbers to and from Qi.f fixed-point format. Pick the integer/fractional bit counts and signed/unsigned, type a value or click individual bits to flip them, and see the stored integer, hex, binary, quantized value, quantization error, resolution and representable range.

Fourier transform (FFT) explorer

Build a time-domain signal from up to three components — each a sine, square, triangle, sawtooth or pulse waveform — and watch the FFT magnitude spectrum of their sum update live. Demonstrates aliasing past the Nyquist frequency, spectral leakage, window functions and FFT bin width.

RF power unit converter

Convert freely between W, mW, µW, dBm and dBW. Edit any field and the rest update live.

LED current-limiting resistor

Calculate the series resistor needed to current-limit an LED, plus the power the resistor will dissipate. Pick a colour for typical V_F values or enter your own.

Low-pass RC filter

Solve f_c = 1/(2πRC) for any one of resistance, capacitance or cutoff frequency in a first-order passive low-pass RC filter.

Microstrip impedance

Compute the characteristic impedance of a microstrip PCB track from its width, copper thickness, substrate height and substrate dielectric constant using the rfcafe approximation.

Moving average filter designer

Interactive simple moving average (SMA) filter designer. Adjust the window size and sampling frequency to see the input/output signals and the resulting magnitude frequency response.

MP4558 design tool

Calculate the passive component values, switching-frequency resistor, inductor, peak inductor current and input/output ripple voltages for a buck converter built around the Monolithic Power MP4558 IC.

NTC thermistor

Beta-equation solver for an NTC thermistor. Pick any one of β, reference resistance R₀, reference temperature T₀, measured resistance R, or measured temperature T to compute from the other four.

Ohm's law (V = IR)

The hammer in every electrical engineer's toolbox. Solve for any one of voltage, current or resistance given the other two.

Op-amp configuration calculator

Pick an op-amp configuration (non-inverting, inverting, buffer, difference or differentiator amplifier), enter the resistor/capacitor values and input voltage(s), and see the gain, output voltage and a live schematic. Assumes an ideal op-amp.

Capacitors in parallel

Compute the total capacitance of two or more capacitors in parallel (C_total = ΣC_i).

Resistors in parallel

Compute the equivalent resistance of two or more resistors in parallel. Accepts metric prefixes (e.g. 10k, 2M2, 470R).

PID spring-mass-damper visualizer

Tune a PID controller (Kp, Ki, Kd) driving a spring-mass-damper plant and watch the mass respond in real time, with the controller's output force drawn on the animation and a live response plot. Drive the setpoint as a step, an alternating square wave, or a slider you drag live; adjust the plant (mass, spring, damping); or jump to under-, critically- and over-damped presets.

Pole-zero explorer (s-plane)

Drag poles and zeros around the continuous-time s-plane and watch the transfer function's Bode magnitude/phase, step response and impulse response update live. Complex poles/zeros auto-mirror their conjugate; right-half-plane poles flag the system as unstable.

Resistor divider

Solve for any one of V_IN, V_OUT, R1 or R2 in a two-resistor voltage divider, given the other three.

3D rotations

Convert a 3D rotation between angle-axis, quaternion, rotation matrix, and intrinsic Euler angles (XYZ, XZY, YXZ, YZX, ZXY, ZYX). Useful for sanity-checking how a rotation is represented across libraries.

Sallen-Key filter designer

Design or analyse a 2nd-order Sallen-Key active filter. Turn a target cut-off frequency, Q and gain into E-series component values (low-pass or high-pass), or enter component values to get f_c, Q and gain — with a live Bode magnitude/phase plot.

Capacitors in series

Compute the total capacitance of two or more capacitors in series (1 / C_total = Σ 1/C_i).

Resistors in series

Compute the equivalent resistance of two or more resistors in series.

555 timer (astable)

Calculate the two timing resistors (R1, R2) and on/off times needed to run a 555 in astable mode at a given output frequency, duty cycle and timing capacitor.

Track current (IPC-2152)

PCB track current carrying capability calculator using the IPC-2152 standard — more accurate than IPC-2221A but requires board thickness, plane proximity and substrate thermal conductivity.

Track current (IPC-2221A)

PCB track current carrying capability calculator using the older IPC-2221A standard. Simpler than IPC-2152 — needs only track thickness, temperature rise, and whether the track is external or internal.

Via current (IPC-2221A)

Maximum current (ampacity), cross-sectional area, electrical and thermal resistance of a PCB via, using the IPC-2221A standard applied to the via's plated annulus.

Via thermal resistance

Top-to-bottom thermal resistance of a PCB via modelled as a hollow copper cylinder. Inputs: via diameter, plating thickness, via height, and copper thermal conductivity.

Wire gauge

Find the minimum AWG gauge wire needed to carry a given DC current with no more than a specified voltage drop across the cable length. Picks the conductor resistivity from a material table or accepts a custom value.