Other Conversions
Everything else: paper, fonts, time zones, batteries and more.
Battery Life Runtime Calculator (mAh)
Calculate how long a battery lasts at a given current draw — mAh to hours, Wh, and screen-on time.
Fertilizer / Nutrient Dilution Calculator
Dilute liquid fertiliser concentrate to target PPM or EC for soil and hydroponics.
Paper Size Converter (A4 / Letter / B-Series / JIS)
Convert between ISO A/B/C, US Letter / Legal / Tabloid and Japanese JIS paper sizes in mm and inches.
Font Size Converter (pt, px, rem, em, %)
Convert font sizes between pt, px, rem, em and % for web and print typography.
Time Zone Overlap Calculator (Remote Teams)
Find overlapping productive hours across up to 8 time zones for distributed teams.
Word Count to Pages Converter (Book / Essay / Manuscript)
Estimate pages from word count across eight standard book and manuscript formats — novel, essay, manuscript, blog.
Podcast Episode Length Optimiser
Recommended podcast episode length by topic and audience plus file size estimates.
Grow Light Distance Calculator
Calculate grow light intensity drop-off (PPFD / lux) by distance using the inverse square law.
Custom Unit Converter (Build Your Own)
Define your own units of measurement and save them — perfect for niche workflows.
Sticker / Decal / Vinyl Size & Cost Calculator
Calculate real-world size from a digital design and sticker cost per unit for Etsy and Cricut sellers.
LED Series Resistor Calculator (Ohm's Law)
Calculate the right series resistor for an LED given supply voltage, forward voltage and current.
Tire Size Comparison Calculator (Plus Sizing)
Compare two tire sizes for diameter, circumference, speedometer error and clearance.
Gear Ratio & Tire Size Regearing Calculator
Calculate speedometer error, RPM change and the new axle gear ratio needed after changing tire size.
What these tools are for
The tools that do not belong to a single hobby, but that people need often enough to be worth having: paper sizes, font and screen measurements, time-zone overlap, battery runtime and a general-purpose custom unit converter.
The paper tools are more useful than they sound because ISO 216 has a property most people never learn — every A size is exactly half the previous one, and the aspect ratio is preserved through every cut, which is why scaling A4 artwork to A3 needs no reframing while converting to US Letter always does.
Time-zone overlap is the one with the most hidden complexity. Offsets are not fixed: daylight saving shifts them on dates that differ by country and change by legislation, so an overlap that holds this week may not hold next month. Check the specific date rather than assuming a pattern.
Which one do I want?
- Scaling artwork between paper sizes
- Paper size converter.
- Finding a meeting time across countries
- Time zone overlap — check the actual date.
- Converting a unit nothing else covers
- Custom unit converter.