Precision Resistor Calculations

Resistora — Professional Resistor Calculation Service

Complex resistor calculations for engineers, developers, and teams. Available as interactive web tools and a programmatic API.

Explore the Tools

Two Ways to Calculate

Use the web interface directly or integrate via API — both backed by the same calculation engine

Web Tools

Six interactive calculators: resistor combination finder, E-series matching, voltage divider design, circuit resistance calculator, and more. No setup required.

API Access

Integrate resistor calculations programmatically. Clean JSON responses, multiple endpoints, and consistent response schemas for use in your applications and workflows.

Calculation Tools

Six specialized tools for resistor and circuit calculations

Resistor Combination Finder

Find optimal resistor combinations for a target resistance value

E-Series Finder

Match target resistance using standard E-series resistor values

Voltage Divider Calculator

Design voltage divider circuits with optimal resistor pairs

Voltage Divider Builder

Calculate output voltage for a given voltage divider circuit

Circuit Calculator

Calculate total resistance for series and parallel circuits

Parallel Resistor Calculator

Quick parallel resistance calculation for two or more resistors

Built For

From individual engineers to large teams — Resistora fits wherever precision matters

Electrical Engineers

Design circuits faster. Find optimal resistor combinations, validate voltage dividers, and verify circuit resistance without manual calculation.

Developers & Integrators

Embed resistor calculations into your applications, design tools, or automated workflows via the API.

Students & Hobbyists

Learn circuit design by experimenting with real combinations. The free plan covers everything you need to get started.

Engineering Teams

Standardize resistor calculation across your team. From BOM validation to design review, get consistent, reproducible results.

Why Resistora

Built for accuracy and reliability — the same standards whether you use the web tools or the API

Fast & Accurate

Multiple proven algorithms find the best combinations quickly. Results are ranked by accuracy so the best match is always first.

Reliable Results

Solutions account for series and parallel configurations across thousands of possible combinations. The free plan already covers most professional use cases.

Consistent Output

Every calculation returns structured results with resistance values, units, circuit topology, and error percentage — predictable whether via UI or API.

Resistora API

Access all Resistora tools programmatically. Integrate resistor calculations into your applications, scripts, and workflows with a clean REST API.

View API Documentation

Ready to Get Started?

All tools are available now. No registration needed.

Start Now