yeast starter calculator

Professional yeast starter calculator for homebrewers and craft brewers. Compute required cells, viability, and optimal starter volume (stir plate, shaken, or no-stir) based on batch size, OG, and style.

Authoritative Data Source and Methodology

Primary references:

  • White, C., & Zainasheff, J. (2010). Yeast: The Practical Guide to Beer Fermentation. Brewers Publications. ISBN: 978-0937381967. https://www.brewerspublications.com/products/yeast
  • Troester, K. (Braukaiser). Yeast Propagation and Pitch Rate (archived). https://web.archive.org/web/20181201000000*/https://braukaiser.com/wiki/index.php/Yeast_Propagation_and_Pitch_Rate
  • White Labs. PurePitch Next Generation Pitching Calculator – Methodology Overview. https://blog.whitelabs.com/purepitch-next-generation-yeast-pitching-calculator

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

SG to Plato: P = -463.37 + 668.72·SG - 205.35·SG^2

Required cells (billions): C_req = (PR × V_mL × P) / 1000

Viability (liquid yeast): v = e^{-0.009·d}

Initial cells (billions): C_init = C_src × v

Growth yield (billions per liter): Y_eff = Y_base × clamp(0.6, 1.4, P_s/9.1)

Starter size (liters): V_s = max(0, (C_req - C_init) / Y_eff)

DME (grams): DME ≈ 100 × V_s × (P_s / 9.1)

Glossary of Variables

  • SG: Specific Gravity (e.g., 1.055)
  • P: Degrees Plato (°P)
  • PR: Pitch rate in million cells per mL per °P
  • V_mL: Batch volume in milliliters
  • C_req: Total cells required (billions)
  • v: Viability fraction (0–1)
  • C_src: Source cells before viability (billions)
  • C_init: Initial viable cells (billions)
  • Y_base: Base growth yield (B/L): 60 (no-stir), 120 (shaken), 180 (stir plate)
  • P_s: Starter wort °P (≈ 9.1 at SG 1.037)
  • V_s: Starter volume (liters)
  • DME: Dry malt extract required for the starter (grams)

How It Works: A Step-by-Step Example

Scenario: 20 L ale at 1.055 with one liquid pack (100B) produced 30 days ago; stir plate; starter wort 1.037.

  1. Convert SG to °P: P ≈ -463.37 + 668.72×1.055 - 205.35×1.055² ≈ 13.6 °P.
  2. Pitch rate: PR = 0.75 M cells/mL/°P → C_req = (0.75 × 20,000 × 13.6)/1000 ≈ 204 B.
  3. Viability (liquid): v = e^{-0.009×30} ≈ 0.763 → C_init ≈ 100 × 0.763 = 76.3 B.
  4. Additional needed: 204 - 76.3 = 127.7 B.
  5. Yield (stir plate): Y_base = 180 B/L; starter °P ≈ 9.1 → Y_eff ≈ 180 B/L.
  6. Starter size: V_s = 127.7 / 180 ≈ 0.71 L. DME ≈ 100 × 0.71 ≈ 71 g.

Frequently Asked Questions (FAQ)

Do I need a starter for dry yeast?

Generally no. Pitch the correct mass of fresh dry yeast (often 20B cells/g at ~97% viability) and rehydrate per the manufacturer’s instructions.

What if my OG is very high?

Increase pitch rate by 10–20% for high gravity wort to improve attenuation and reduce stress. The “Custom” option lets you set an exact value.

Can I split the starter into steps?

Yes. If the single-step volume is too large for your flask, run a smaller first step, chill and decant, then step up again. This tool suggests a 2-step plan automatically.

How accurate is viability from pack date?

It’s an estimate based on published decay curves. Storage conditions and handling can increase variance; when possible, use a cell counter for critical batches.

What starter gravity should I use?

1.036–1.040 (≈9–10 °P) is a widely recommended range for healthy propagation. The tool adjusts yield for different starter gravities within 7–12 °P.

Does oxygenation change the result?

Proper oxygenation improves growth and yeast health but is not directly modeled here. Values assume typical aeration for each method.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
','
Formula (extracted text)
SG to Plato: P = -463.37 + 668.72·SG - 205.35·SG^2 Required cells (billions): C_req = (PR × V_mL × P) / 1000 Viability (liquid yeast): v = e^{-0.009·d} Initial cells (billions): C_init = C_src × v Growth yield (billions per liter): Y_eff = Y_base × clamp(0.6, 1.4, P_s/9.1) Starter size (liters): V_s = max(0, (C_req - C_init) / Y_eff) DME (grams): DME ≈ 100 × V_s × (P_s / 9.1)
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Full original guide (expanded)

Authoritative Data Source and Methodology

Primary references:

  • White, C., & Zainasheff, J. (2010). Yeast: The Practical Guide to Beer Fermentation. Brewers Publications. ISBN: 978-0937381967. https://www.brewerspublications.com/products/yeast
  • Troester, K. (Braukaiser). Yeast Propagation and Pitch Rate (archived). https://web.archive.org/web/20181201000000*/https://braukaiser.com/wiki/index.php/Yeast_Propagation_and_Pitch_Rate
  • White Labs. PurePitch Next Generation Pitching Calculator – Methodology Overview. https://blog.whitelabs.com/purepitch-next-generation-yeast-pitching-calculator

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

SG to Plato: P = -463.37 + 668.72·SG - 205.35·SG^2

Required cells (billions): C_req = (PR × V_mL × P) / 1000

Viability (liquid yeast): v = e^{-0.009·d}

Initial cells (billions): C_init = C_src × v

Growth yield (billions per liter): Y_eff = Y_base × clamp(0.6, 1.4, P_s/9.1)

Starter size (liters): V_s = max(0, (C_req - C_init) / Y_eff)

DME (grams): DME ≈ 100 × V_s × (P_s / 9.1)

Glossary of Variables

  • SG: Specific Gravity (e.g., 1.055)
  • P: Degrees Plato (°P)
  • PR: Pitch rate in million cells per mL per °P
  • V_mL: Batch volume in milliliters
  • C_req: Total cells required (billions)
  • v: Viability fraction (0–1)
  • C_src: Source cells before viability (billions)
  • C_init: Initial viable cells (billions)
  • Y_base: Base growth yield (B/L): 60 (no-stir), 120 (shaken), 180 (stir plate)
  • P_s: Starter wort °P (≈ 9.1 at SG 1.037)
  • V_s: Starter volume (liters)
  • DME: Dry malt extract required for the starter (grams)

How It Works: A Step-by-Step Example

Scenario: 20 L ale at 1.055 with one liquid pack (100B) produced 30 days ago; stir plate; starter wort 1.037.

  1. Convert SG to °P: P ≈ -463.37 + 668.72×1.055 - 205.35×1.055² ≈ 13.6 °P.
  2. Pitch rate: PR = 0.75 M cells/mL/°P → C_req = (0.75 × 20,000 × 13.6)/1000 ≈ 204 B.
  3. Viability (liquid): v = e^{-0.009×30} ≈ 0.763 → C_init ≈ 100 × 0.763 = 76.3 B.
  4. Additional needed: 204 - 76.3 = 127.7 B.
  5. Yield (stir plate): Y_base = 180 B/L; starter °P ≈ 9.1 → Y_eff ≈ 180 B/L.
  6. Starter size: V_s = 127.7 / 180 ≈ 0.71 L. DME ≈ 100 × 0.71 ≈ 71 g.

Frequently Asked Questions (FAQ)

Do I need a starter for dry yeast?

Generally no. Pitch the correct mass of fresh dry yeast (often 20B cells/g at ~97% viability) and rehydrate per the manufacturer’s instructions.

What if my OG is very high?

Increase pitch rate by 10–20% for high gravity wort to improve attenuation and reduce stress. The “Custom” option lets you set an exact value.

Can I split the starter into steps?

Yes. If the single-step volume is too large for your flask, run a smaller first step, chill and decant, then step up again. This tool suggests a 2-step plan automatically.

How accurate is viability from pack date?

It’s an estimate based on published decay curves. Storage conditions and handling can increase variance; when possible, use a cell counter for critical batches.

What starter gravity should I use?

1.036–1.040 (≈9–10 °P) is a widely recommended range for healthy propagation. The tool adjusts yield for different starter gravities within 7–12 °P.

Does oxygenation change the result?

Proper oxygenation improves growth and yeast health but is not directly modeled here. Values assume typical aeration for each method.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
','
Formula (extracted text)
SG to Plato: P = -463.37 + 668.72·SG - 205.35·SG^2 Required cells (billions): C_req = (PR × V_mL × P) / 1000 Viability (liquid yeast): v = e^{-0.009·d} Initial cells (billions): C_init = C_src × v Growth yield (billions per liter): Y_eff = Y_base × clamp(0.6, 1.4, P_s/9.1) Starter size (liters): V_s = max(0, (C_req - C_init) / Y_eff) DME (grams): DME ≈ 100 × V_s × (P_s / 9.1)
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Authoritative Data Source and Methodology

Primary references:

  • White, C., & Zainasheff, J. (2010). Yeast: The Practical Guide to Beer Fermentation. Brewers Publications. ISBN: 978-0937381967. https://www.brewerspublications.com/products/yeast
  • Troester, K. (Braukaiser). Yeast Propagation and Pitch Rate (archived). https://web.archive.org/web/20181201000000*/https://braukaiser.com/wiki/index.php/Yeast_Propagation_and_Pitch_Rate
  • White Labs. PurePitch Next Generation Pitching Calculator – Methodology Overview. https://blog.whitelabs.com/purepitch-next-generation-yeast-pitching-calculator

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

SG to Plato: P = -463.37 + 668.72·SG - 205.35·SG^2

Required cells (billions): C_req = (PR × V_mL × P) / 1000

Viability (liquid yeast): v = e^{-0.009·d}

Initial cells (billions): C_init = C_src × v

Growth yield (billions per liter): Y_eff = Y_base × clamp(0.6, 1.4, P_s/9.1)

Starter size (liters): V_s = max(0, (C_req - C_init) / Y_eff)

DME (grams): DME ≈ 100 × V_s × (P_s / 9.1)

Glossary of Variables

  • SG: Specific Gravity (e.g., 1.055)
  • P: Degrees Plato (°P)
  • PR: Pitch rate in million cells per mL per °P
  • V_mL: Batch volume in milliliters
  • C_req: Total cells required (billions)
  • v: Viability fraction (0–1)
  • C_src: Source cells before viability (billions)
  • C_init: Initial viable cells (billions)
  • Y_base: Base growth yield (B/L): 60 (no-stir), 120 (shaken), 180 (stir plate)
  • P_s: Starter wort °P (≈ 9.1 at SG 1.037)
  • V_s: Starter volume (liters)
  • DME: Dry malt extract required for the starter (grams)

How It Works: A Step-by-Step Example

Scenario: 20 L ale at 1.055 with one liquid pack (100B) produced 30 days ago; stir plate; starter wort 1.037.

  1. Convert SG to °P: P ≈ -463.37 + 668.72×1.055 - 205.35×1.055² ≈ 13.6 °P.
  2. Pitch rate: PR = 0.75 M cells/mL/°P → C_req = (0.75 × 20,000 × 13.6)/1000 ≈ 204 B.
  3. Viability (liquid): v = e^{-0.009×30} ≈ 0.763 → C_init ≈ 100 × 0.763 = 76.3 B.
  4. Additional needed: 204 - 76.3 = 127.7 B.
  5. Yield (stir plate): Y_base = 180 B/L; starter °P ≈ 9.1 → Y_eff ≈ 180 B/L.
  6. Starter size: V_s = 127.7 / 180 ≈ 0.71 L. DME ≈ 100 × 0.71 ≈ 71 g.

Frequently Asked Questions (FAQ)

Do I need a starter for dry yeast?

Generally no. Pitch the correct mass of fresh dry yeast (often 20B cells/g at ~97% viability) and rehydrate per the manufacturer’s instructions.

What if my OG is very high?

Increase pitch rate by 10–20% for high gravity wort to improve attenuation and reduce stress. The “Custom” option lets you set an exact value.

Can I split the starter into steps?

Yes. If the single-step volume is too large for your flask, run a smaller first step, chill and decant, then step up again. This tool suggests a 2-step plan automatically.

How accurate is viability from pack date?

It’s an estimate based on published decay curves. Storage conditions and handling can increase variance; when possible, use a cell counter for critical batches.

What starter gravity should I use?

1.036–1.040 (≈9–10 °P) is a widely recommended range for healthy propagation. The tool adjusts yield for different starter gravities within 7–12 °P.

Does oxygenation change the result?

Proper oxygenation improves growth and yeast health but is not directly modeled here. Values assume typical aeration for each method.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
','
Formula (extracted text)
SG to Plato: P = -463.37 + 668.72·SG - 205.35·SG^2 Required cells (billions): C_req = (PR × V_mL × P) / 1000 Viability (liquid yeast): v = e^{-0.009·d} Initial cells (billions): C_init = C_src × v Growth yield (billions per liter): Y_eff = Y_base × clamp(0.6, 1.4, P_s/9.1) Starter size (liters): V_s = max(0, (C_req - C_init) / Y_eff) DME (grams): DME ≈ 100 × V_s × (P_s / 9.1)
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn
Formulas

(Formulas preserved from original page content, if present.)

Version 0.1.0-draft
Citations

Add authoritative sources relevant to this calculator (standards bodies, manuals, official docs).

Changelog
  • 0.1.0-draft — 2026-01-19: Initial draft (review required).