LED Series Resistor Scenario Calculator

How to use LED Series Resistor Scenario Calculator

Required resistance is (supply−entered forward drop)/target current. Optional E12 rounding selects an upward preferred nominal value, then actual model current and resistor dissipation are recomputed.

1. Enter supply voltage (v), entered forward drop (v), target current (a).
2. Choose the stated convention and check the units and supported model.
3. Calculate, inspect the result, then copy or download it.

Good to know

• Positive target current, nonnegative forward drop and supply above that drop. User component assumptions only; no recommended safe rating, thermal margin or real LED protection guarantee.
• Runs locally. Text/JSON fields are capped at30,000 characters; stricter page-specific and numeric-string limits also apply. Numeric inputs are bounded to magnitude1e15 and nonzero magnitude at least1e-100 unless an exact-string mode states otherwise. Approximate summaries use12 significant digits; CSV numeric cells retain the complete stored value and potentially formula-like string cells gain a protective apostrophe; unsupported, non-finite or detected underflow states return an error.