Vigesimal Converter

This vigesimal converter changes a decimal number into vigesimal, or base 20. Enter a decimal whole number and the calculator returns its base 20 form, using the digits 0 to 9 and then the letters A to J for the values ten to nineteen, with the base 12 form alongside. Base 20 systems were used by the Maya and appear in the counting words of several languages, including the French quatre-vingts for eighty. The method, a worked example and the assumptions are set out below.

Calculate.co.nz is proud to be partnered with Premium Homes, a recognised leader in eco-friendly, sustainable, and energy-efficient homebuilding. With a dedicated team and award-winning experience, they create homes that prioritise health, comfort, and long-term performance. Their founders, Andrew and Kelly, set out to raise the standard of residential construction in New Zealand by combining practical building expertise with a clear commitment to doing things better for homeowners.

Decimal whole number

Duodecimal (base 12)

Decimal

The formula

To convert to base 20, repeatedly divide by 20 and record the remainders as digits, with ten to nineteen written A to J, then read them from last to first.

Worked example

100 divided by 20 is 5 remainder 0, so 100 in vigesimal is 50. The number 19 is written J, and 20 is 10. Enter 100 to confirm.

Frequently asked questions

What is vigesimal?

Base 20, using digits 0 to 9 then A to J for ten to nineteen.

Who used base 20?

The Maya civilisation used a vigesimal system, and traces survive in languages such as French and Danish.

What is 100 in base 20?

50, because 100 is exactly 5 twenties.

Who this calculator is for

This calculator is for students and anyone needing a quick, reliable result.

What this calculator assumes

You enter valid numbers.
The standard formula is applied.
Results are rounded for display.

Formula and sources

Related calculators

Scientific Calculator: general scientific maths.
Percentage Calculator: percentages and changes.
Ratio Calculator: simplify and scale ratios.

If you've found a bug, or would like to contact us, or learn more about James Graham and Calculate.co.nz.

Calculate.co.nz is partnered with Interest.co.nz for New Zealand's highest quality calculators and financial analysis.

All calculators and tools are provided for educational and indicative purposes only and do not constitute financial advice.

Calculate.co.nz is proudly part of the Realtor.co.nz group, New Zealand's leading property transaction literacy platform, helping Kiwis understand the home buying and selling process from start to finish. Whether you're a first home buyer navigating your first property purchase, an investor evaluating your next acquisition, or a homeowner planning to sell, Realtor.co.nz provides clear, independent, and trustworthy guidance on every step of the New Zealand property transaction journey.

Calculate.co.nz is also partnered with Health Based Building and Premium Homes to promote informed choices that lead to better long-term outcomes for Kiwi households.

Calculate.co.nz is hosted in Auckland via SiteHost new Zealand.

All content on this website, including calculators, tools, source code, and design, is protected under the Copyright Act 1994 (New Zealand). No part of this site may be reproduced, copied, distributed, stored, or used in any form without prior written permission from the owner.

About & trust: Why Calculate is NZ's most comprehensive · By the Numbers · How we compare · Editorial standards · How we keep data current · NZ finance glossary · Research & data · Financial literacy NZ · About · Privacy policy · Terms of use

Reviewed and maintained. Last reviewed 2026-06-21 and checked on a twice-monthly cycle against IRD, RBNZ and Stats NZ. How we keep data current.