| What it does | Electronics calculators for makers
| Free calculators and guides for business, marketing, SaaS, ecommerce, real estate, restaurants and software decisions
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| Key features | - Resistor Color Code: read 4, 5 and 6-band resistors or find bands for a value
- LED Resistor: pick the current-limiting resistor and power rating
- Voltage Divider: output voltage, loading effect, or solve R2 for target Vout
- RC Filter: cutoff frequency, time constant and attenuation at any frequency
- LC Resonance: resonant frequency, characteristic impedance and Q
- 555 Timer: astable frequency/duty cycle and monostable pulse width
- Battery Life: runtime from capacity, active/sleep current and duty cycle
- PCB Trace Width: IPC-2221 trace width for current and temperature rise
- Electronics Unit Converter: SI prefixes, AWG to mm², mil to mm, dBm to mW, oz copper
| - 42 free calculators across ROI, marketing, SaaS, ecommerce, real estate, restaurant and software categories
- Transparent formulas with explanations and examples for each calculation
- Decision-focused results emphasizing practical metrics like ROI, ROAS, profit, margin, payback, CAC and LTV
- Browser-based calculations with optional account signup to save and export reports
- Downloadable and printable reports in multiple formats including PDF, CSV and images
- Practical guides accompanying each calculator with assumptions and business context
- Responsive design optimized for phones, tablets, laptops and desktops
- Popular calculators including SEO ROI, Google Ads ROI, SaaS LTV:CAC, MRR, ARR and NRR metrics
- Covers multiple business use cases including marketing, SaaS, ecommerce, real estate and restaurants
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| What makes it different | - Real E-series resistor values, not ideal numbers
- Engineering notation input and result sharing as links
- No ads, no tracking, no sign-up for free calculators
- Whole-device BOM costing and battery-life summary in Pro
- Works on phone at the bench
| - Clear explanations and context instead of just numbers from calculators
- No signup required for basic calculator use
- Consistent interface across all calculators designed for real business decisions
- Educational content showing assumptions and examples for each calculation
- Brings scattered business metrics into one unified platform
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Ohmlark
SolveIndex