What does '1:10 dilution' mean?

In modern lab shorthand, a 1:10 dilution takes 1 part stock into 10 parts total final volume — i.e. 1 part stock plus 9 parts diluent. So 100 µL of stock + 900 µL of diluent = 1000 µL of 1:10 diluted solution, and the concentration drops by a factor of 10. This is the 'parts of final' convention Harris (QCA 10e §1-3) and most cell-biology and molecular-biology protocols follow.

How is the dilution factor different from a concentration ratio?

The dilution factor is dimensionless: DF = C_stock / C_final = V_final / V_stock. It only tells you how much less concentrated the final solution is. A concentration ratio also names the units (e.g. '2 mg/mL to 0.2 mg/mL') and lets you check DF directly. Both agree numerically — DF = 10 for a 2 → 0.2 mg/mL dilution — but DF drops the units so it works across mM, µM, and %(w/v) alike.

When should I use a serial dilution instead?

When a single-step dilution would need a stock volume below your pipette's reliable range (~1 µL on a P2, ~10 µL on a P200). A DF of 10 000 in one step from 10 mL final volume means pipetting 1 µL — barely inside a P2's range. Two 1:100 serial steps land you in the same place with 10 µL pipettes on both steps, well within reliable range. Use the serial dilution calculator for a step plan.

Is '1:10' the same as 'stock:diluent' or 'stock:final'?

There are two conventions and they disagree. This calculator (and Harris QCA, molecular biology protocols, and most journals) uses stock:final — 1:10 means 1 mL stock brought up to 10 mL total, i.e. 1 mL + 9 mL diluent. Some analytical-chemistry references use stock:diluent — 1:10 means 1 mL stock + 10 mL diluent, i.e. 11 mL total. Always read the source to check which convention is in play; when in doubt, cite the volumes explicitly.

Dilution Factor Calculator — DF, 1:N Ratios & Volumes

The dilution factor (DF) is the ratio by which a stock’s concentration drops when you dilute it. It is the calculator you reach for when you know the final volume you want and the “1:N” ratio from a protocol, but do not need the absolute concentration — only how much stock to pipette and how much diluent to add.

Dilution Factor Calculator

Enter any two of DF, V_stock, V_final and pick which to solve for. Also emits the 1:N ratio and the diluent volume needed.

Equations used

DF = V_final / V_stock, rearranged for each variable:

D F = \frac{V _{final}}{V _{stock}}

V_{stock} = \frac{V _{final}}{D F}

V_{final} = D F \cdot V_{stock}

The equation

The dilution factor is defined as:

$DF = \frac{C_\text{stock}}{C_\text{final}} = \frac{V_\text{final}}{V_\text{stock}}$

The two forms are equivalent because moles are conserved: C_stock · V_stock = C_final · V_final. When you write it as a ratio of volumes, all the concentration units cancel — DF is dimensionless. In wet-lab practice it is written as parts notation: DF = 10 → “1:10”, DF = 100 → “1:100”.

Rearranged for each variable:

Stock volume: V_stock = V_final / DF
Final volume: V_final = DF · V_stock
Diluent volume: V_diluent = V_final − V_stock

Worked example

A common bench task: prepare 1.0 mL of a 1:100 dilution of a stock antibody.

Worked example — 1:100 dilution to 1.0 mL

DF (from 1:100): 100
V_final (target): 1.0 mL = 1000 µL

Formula
$V_{stock} = \frac{V _{final}}{D F}$
Substitute
$V_{stock} = 1000/100$
Note
Pipette 10 µL of stock into a tube, then add 990 µL of diluent (buffer/water/media as the protocol says) and mix. Final volume is exactly 1.0 mL; the concentration is 1/100 of the stock. Below 10 µL, single-step dilutions start losing pipette accuracy — see 'When to switch to a serial dilution' below.
Result
$V_{stock} = 10 μ L, V_{diluent} = 990 μ L$

Parts notation vs stock:diluent

“1:N” is the most common shorthand for a dilution, but two conventions coexist:

stock:final (this calculator, Harris QCA, most cell / molecular biology protocols): “1:10” means 1 part stock brought up to 10 parts total — 1 µL stock + 9 µL diluent = 10 µL final.
stock:diluent (some analytical-chemistry and immunology antibody vendors): “1:10” means 1 part stock + 10 parts diluent — 1 µL stock + 10 µL diluent = 11 µL final.

The two disagree by DF vs DF + 1. For DF = 10 the difference is 10 % — the wrong convention gives you a solution that is 10 % too concentrated. When a protocol is ambiguous, cite the volumes explicitly (“10 µL into 1 mL final”) instead of the ratio.

When to switch to a serial dilution

Single-step dilutions are pipette-limited: a P2 (0.2–2 µL) is only reliable down to ~1 µL, a P10 (1–10 µL) down to ~2 µL, and a P200 (20–200 µL) down to ~20 µL. Anything below those numbers should be broken into two or more steps. Rule of thumb:

DF ≤ 20 → single step is fine even from a 50 µL final volume.
DF = 100 → single step works at ≥ 100 µL final volume (pipette 1–2 µL of stock).
DF ≥ 1000 → use a serial dilution (two 1:32 steps or two 1:100 steps, depending on tube volumes). Use the serial dilution calculator for a step-by-step plan.

Common pitfalls

“1:10” can mean two different things. Confirm the convention (stock:final vs stock:diluent) before you pipette; this calculator uses stock:final.
Diluent is not the final volume. V_diluent = V_final − V_stock. A “1:10 in 1 mL” is 100 µL stock + 900 µL diluent, not 1000 µL diluent.
Pipette floor. Nothing checks that V_stock is above your pipette’s reliable minimum. If DF and V_final give you 0.3 µL, redesign as a serial dilution.
DF < 1 is not a dilution. It’s a concentration-up, which you cannot do by adding more solvent. This calculator rejects DF < 1 with a clear error.

Practice problems

Attempt each on paper, then expand the worked solution to check your arithmetic and sig-figs.

Problem 1 Easy You take 100 µL of stock and bring it up to 1000 µL final volume. What is the dilution factor?

Answer: DF = 10 (1:10 dilution)

Solve for DF

V_stock: 100 µL
V_final: 1000 µL

Formula
$D F = \frac{V _{final}}{V _{stock}}$
Substitute
$D F = 1000/100$
Note
Since V_stock and V_final share a unit (µL), DF cancels units and is dimensionless. Diluent = 1000 − 100 = 900 µL.
Result
$D F = 10 (1 : 10)$

Problem 2 Easy A protocol says '1:100 dilution in a 500 µL final volume'. How much stock do you pipette?

Answer: 5 µL of stock

Solve for V_stock

DF (from 1:100): 100
V_final: 500 µL

Formula
$V_{stock} = \frac{V _{final}}{D F}$
Substitute
$V_{stock} = 500/100$
Note
5 µL stock + 495 µL diluent = 500 µL total. 5 µL is at the low end of a P10 pipette; if precision matters, dilute the stock 1:10 first (a serial step) and pipette 50 µL of that intermediate.
Result
$V_{stock} = 5 μ L$

Problem 3 Intermediate You have 10 µL of stock. If you want a 1:50 dilution, what final volume do you prepare?

Answer: 500 µL final (490 µL diluent)

Solve for V_final

DF (from 1:50): 50
V_stock: 10 µL

Formula
$V_{final} = D F \cdot V_{stock}$
Substitute
$V_{final} = 50 \cdot 10$
Note
Add 490 µL diluent to 10 µL stock, or bring 10 µL up to the 500 µL mark in a graduated tube. Note DF = 50 means the final concentration is 1/50 of the stock concentration.
Result
$V_{final} = 500 μ L$

Problem 4 Hard You mixed 40 µL of 5 mg/mL antibody with 160 µL of diluent. What is the dilution factor and the final concentration?

Answer: DF = 5 (1:5), final = 1.0 mg/mL

Solve for DF, then apply to concentration

V_stock: 40 µL
V_diluent: 160 µL
V_final = V_stock + V_diluent: 200 µL
C_stock: 5 mg/mL

Formula
$D F = \frac{V _{final}}{V _{stock}}; C_{final} = \frac{C _{stock}}{D F}$
Substitute
$D F = 200/40 = 5; C_{final} = 5/5$
Note
The mixing gives 200 µL of a 1:5 dilution — the concentration drops by the same factor of 5. This is the fastest way to reason about mix-then-check protocols without solving C₁V₁ = C₂V₂ end-to-end.
Result
$D F = 5 (1 : 5), C_{final} = 1.0 mg/mL$

Frequently asked questions

What does '1:10 dilution' mean?: In modern lab shorthand, a 1:10 dilution takes 1 part stock into 10 parts total final volume — i.e. 1 part stock plus 9 parts diluent. So 100 µL of stock + 900 µL of diluent = 1000 µL of 1:10 diluted solution, and the concentration drops by a factor of 10. This is the 'parts of final' convention Harris (QCA 10e §1-3) and most cell-biology and molecular-biology protocols follow.
How is the dilution factor different from a concentration ratio?: The dilution factor is dimensionless: DF = C_stock / C_final = V_final / V_stock. It only tells you how much less concentrated the final solution is. A concentration ratio also names the units (e.g. '2 mg/mL to 0.2 mg/mL') and lets you check DF directly. Both agree numerically — DF = 10 for a 2 → 0.2 mg/mL dilution — but DF drops the units so it works across mM, µM, and %(w/v) alike.
When should I use a serial dilution instead?: When a single-step dilution would need a stock volume below your pipette's reliable range (~1 µL on a P2, ~10 µL on a P200). A DF of 10 000 in one step from 10 mL final volume means pipetting 1 µL — barely inside a P2's range. Two 1:100 serial steps land you in the same place with 10 µL pipettes on both steps, well within reliable range. Use the serial dilution calculator for a step plan.
Is '1:10' the same as 'stock:diluent' or 'stock:final'?: There are two conventions and they disagree. This calculator (and Harris QCA, molecular biology protocols, and most journals) uses stock:final — 1:10 means 1 mL stock brought up to 10 mL total, i.e. 1 mL + 9 mL diluent. Some analytical-chemistry references use stock:diluent — 1:10 means 1 mL stock + 10 mL diluent, i.e. 11 mL total. Always read the source to check which convention is in play; when in doubt, cite the volumes explicitly.

Sources

Harris, Quantitative Chemical Analysis, 10th ed. (2020), §1-3
Cold Spring Harbor Protocols — Dilutions: A Review
IUPAC Gold Book — dilution

Last updated: 2026-09-18.