# [Estimate a rectangular project from a weighed sample](https://threadcabin.com/explore/63/estimate-a-rectangular-project-from-a-weighed-sample)

> A finished 10 × 10 cm sample weighing 5 g scales to 150 g for a 50 × 60 cm rectangle. With 10% reserve, plan 165 g before rounding packages.

- Canonical page: https://threadcabin.com/explore/63/estimate-a-rectangular-project-from-a-weighed-sample
- Language: en
- Published: 2026-09-25T17:26:32.8672207+00:00
- Updated: 2026-09-25T17:26:38.2014122+00:00
- Primary image: [Estimate a rectangular project from a weighed sample — measured quantities](https://threadcabin.com/images/learning/s32-plan.png)

A finished 10 × 10 cm sample weighing 5 g scales to 150 g for a 50 × 60 cm rectangle. With 10% reserve, plan 165 g before rounding packages.

## Work through the example

1. Make and finish the sample in the actual stitch pattern. Weigh it dry on a scale precise enough for the sample; exclude unrelated labels and supports.
2. Compare areas: 3,000 cm² ÷ 100 cm² = 30. At 200 m per 50 g, the base length is 600 m and the reserved length is 660 m.
3. The same 50 g package requires four balls, or 200 g. Use the transfer button when trying another yarn label; it carries 600 m and the 10% reserve separately.

## Check before committing

The estimate assumes uniform rectangular fabric. Borders, seams, shaping, cables and different stitch textures need their own samples and quantities.

## Method and sources

These are original planning examples using the linked tools’ methods. Replace measured inputs with your own samples; a calculator cannot validate the construction. Keep the resulting measurements, choices and remaining checks with the project.

- [Craft Yarn Council: Standard Yarn Weight System](https://www.craftyarncouncil.com/standards/yarn-weight-system)
- [Craft Yarn Council: Hooks & Needles](https://craftyarncouncil.com/standards/hooks-and-needles)

[Report a correction](/corrections).

[Browse editable craft templates](/crafts)

## Sources and provenance

- [Gauge is a fabric measurement, not a needle promise](https://threadcabin.com/explore/2/gauge-is-a-fabric-measurement-not-a-needle-promise)
- [Swatch-based yarn estimator](https://threadcabin.com/tools/swatch-yarn-estimator)
- [Yarn substitution planner](https://threadcabin.com/tools/yarn-substitution-planner)

## [Swatch-based yarn estimator](https://threadcabin.com/tools/swatch-yarn-estimator)

Estimate yarn for a uniform flat piece from the area and weight of your own washed swatch.

Weigh a dry finished sample without needles, pins or attached extra yarn. Measure only the area represented by that mass.  Target width × height describes a rectangle in the same stitch pattern; sleeves, seams, borders and other structures need separate samples or component estimates.

The target area is divided by the swatch area, then multiplied by swatch weight and allowance. Label length and weight convert that estimate to yarn length and whole balls. A visible ±15% planning band shows sensitivity, not a statistical guarantee. Use only for similarly constructed rectangular fabric with matching stitch pattern, gauge, and density.

- Swatch width: 10 cm
- Swatch height: 10 cm
- Swatch weight: 5 g
- Target width: 50 cm
- Target height: 60 cm
- Weight per ball: 50 g
- Length per ball: 200 m
- Extra allowance: 10 %

## [Yarn substitution planner](https://threadcabin.com/tools/yarn-substitution-planner)

Turn required yarn length into whole substitute balls, total length, and weight.

Use the original total length, or original ball count × length per ball, then enter the replacement label length. Equal ball weights do not imply equal lengths.  Read quantity and suitability separately: enough yarn may still give the wrong fabric. Confirm washed gauge, drape and care before committing.

Required length plus allowance is divided by substitute length per ball and rounded up. Risk also reflects fiber, yarn structure, blocked gauge, weight category, care, and drape; unknown or different properties require a swatch before purchasing.

- How is the original quantity given?: Total required length
- Number of original balls: 3
- Length per ball: 200 m
- Required length: 600 m
- Substitute length per ball: 150 m
- Weight per ball: 50 g
- Extra allowance: 10 %