Electronics Calculators

Electronics calculators for design and repair

These tools cover the everyday maths of electronic design — the calculations you reach for at the bench, while laying out a PCB, or when checking a circuit before you power it up. They're grouped by job: basic passive networks like the Ohm's Lawand voltage dividercalculators; timing and filtering with theRC time constant and555 timer tools; AC and RF work; power and regulator design; and a set of PCB and wiring calculators for trace width, impedance, and copper.

Each calculator explains the formula it uses, works live as you type, and includes a worked example so you can check your own numbers. Several also double as references — theE-series values,resistor colour codes, andcapacitor codes pages let you look values up as well as calculate them. Where a result depends on real-world factors like temperature or copper quality, the page says so rather than pretending a formula is the final word.

Standards, and where they stop

Several of these calculators implement a published standard rather than pure physics, and it matters that you know which. Trace current sizing follows IPC-2221, a conservative empirical curve derived from measurements — it knows nothing about your copper pour, your via stitching, or the airflow over the board. Platinum RTD linearisation follows IEC 60751 and its Callendar-Van Dusen coefficients. Standard component values follow theE-series, where the published lists for E3 through E24 are historical and differ slightly from what the formula produces: 2.7 rather than 2.61, 8.2 rather than 8.25.

Where a page follows a standard it says so, because that tells you when the answer is authoritative and when it is a starting point. A trace current figure is a sanity check before you commit to a stackup, not a substitute for thermal analysis on a board that runs hot.

A note on tolerance

Almost every result here is more precise than the parts you will build with. A 1% resistor and a 20% electrolytic put a floor under how much the arithmetic can tell you, and an NTC thermistor's beta value drifts between batches. Use these tools to choose a value and to understand the sensitivity — what happens if this resistor is 5% high — rather than to chase a fourth significant figure the bill of materials cannot deliver.