---
title: "JAS Log Scale Calculator (Japanese Agricultural Standard)"
description: "Scale logs to the JAS rule with diameter rounding and ovality — free."
image: "https://nestingcalc.com/og-default.png"
url: "https://nestingcalc.com/jas-log-scale-calculator/"
locale: "en"
---

# JAS Log Scale Calculator (Japanese Agricultural Standard)

Scale logs to the JAS rule with diameter rounding and ovality — free.

Enter the short-axis diameter and length; the JAS calculator applies the official rounding (floor to 1 cm below 14 cm, to even 2 cm above), handles oval logs and lengths over 6 m, and totals a load with quantity.

Interactive calculator (open in browser): [https://nestingcalc.com/jas-log-scale-calculator/](https://nestingcalc.com/jas-log-scale-calculator/)

## FAQ

How does JAS round the diameter?

Below 14 cm the diameter is floored to whole centimetres; at 14 cm and above it is floored to the next even 2 cm — for example 25.9 cm scales to 24 cm. Volume is D² × L ÷ 10 000, rounded to 3 decimals.

What changes for logs longer than 6 m?

A length allowance is added to the scaled diameter: D\_used = D + (floor(L) − 4) ÷ 2 in cm. A 30 cm log of 7.6 m is scaled with 31.5 cm and gives 0.754 m³.

How are oval logs scaled?

Measure both axes, scale each with the rounding rule and average them. For a short axis of 14–40 cm add 2 cm for every 6 cm difference between the axes (2 cm per 8 cm above 40 cm) — enable the adjustment above.

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    Calculate Hoppus volume, true volume and Hoppus tons for round logs — free.

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-   [Timber Unit Converter (m³, BF, MBF, Hoppus)](https://nestingcalc.com/timber-unit-converter/)

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-   [Sawmill Recovery Calculator](https://nestingcalc.com/sawmill-recovery-calculator/)

    Lumber recovery rate and log-rule overrun — benchmarked against FAO and EU data.

## Related guides

-   [JAS Log Scaling: The Japanese Agricultural Standard Explained](https://nestingcalc.com/guides/jas-log-grading-standard/)

    How JAS scales round logs: the 1 cm / 2 cm diameter rounding rule, V = D² × L ÷ 10,000, the long-log adjustment, the oval-log rule, and why Asia-Pacific plantation trade quotes JAS cubic metres.

-   [How to Calculate Board Feet (and Log Scaling Rules)](https://nestingcalc.com/guides/how-to-calculate-board-feet/)

    The board foot is how lumber is bought and sold. The formula takes a minute; the scaling rules and pricing traps take a bit more.

-   [The Material Order Checklist: Before You Buy Steel, Wood or Tile](https://nestingcalc.com/guides/material-order-checklist/)

    Ten minutes of checking before the order saves a second trip to the supplier.

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