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Free electronics calculators for resistor codes, LED resistors, voltage dividers, filters, 555 timers, battery runtime and PCB trace widths with no ads
Ohmlark provides fast, accurate electronics calculators for makers and hardware builders. The free calculators include resistor color code reader and finder, LED current-limiting resistor selector, voltage divider solver, RC and LC filter design, 555 timer configuration, battery life estimator, and IPC-2221 PCB trace width calculator, plus an electronics unit converter. Results snap to real E-series resistor values rather than ideal numbers. Every field accepts engineering notation like 4k7, 100n, or 20mA, shows what it understood, and any result can be copied or shared as a link.
Pro adds whole-device bill of materials costing per board and per batch with unlimited rows, battery-life summaries across all components, PDF and CSV export, saved projects with optional encrypted sync across browsers, component library management, and priority email support. Pro costs $4 per month or $29 one-time for lifetime access.
Pricing model: Freemium
Free: $0 forever. Pro Monthly: $4 per month, cancel anytime. Pro Lifetime: $29 one-time payment.
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Pro Monthly is $4 per month and renews automatically until you cancel. Pro Lifetime is a one-time $29 payment for access as long as Ohmlark operates, including all future features. Lifetime costs less if you expect to use Pro for more than about seven months.
Ohmlark has no accounts. After checkout you return to Ohmlark with Pro switched on and the key shown on the page. The key is also emailed by Creem and shown on your account page. On a new device or browser, open ohmlark.com/restore and paste the key.
Yes, your license is personal and you may use it on your own browsers and devices. Open ohmlark.com/restore in the other browser, paste your license key and select Unlock Pro. Pro is remembered with a single cookie per browser. Each key can be activated in a limited number of browsers, and you can release an activation from the account page.
Yes, within 14 days of your first payment for either Monthly or Lifetime. Email hello@ohmlark.com with your order email or license key for a full refund with no questions asked. Monthly renewal payments are generally not refunded.
Pro Monthly is $4 per month. It renews automatically each month until you cancel, and you can cancel at any time. Pro Lifetime is a one-time payment of $29 for access for as long as Ohmlark is operated, including all future Pro features. If you expect to use Pro for more than about seven months, Lifetime costs less. Prices are in USD. Taxes may apply and are calculated at checkout by Creem, our Merchant of Record.
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Ohmlark has a free listing. The owner can unlock the full profile with a paid launch for $5:
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