What is a Scoville Heat Unit (SHU)?

A Scoville Heat Unit is the dilution factor at which capsaicin can no longer be detected by a trained taster panel. A jalapeño at 8,000 SHU means the juice must be diluted 8,000 times before heat is imperceptible. Modern labs measure capsaicin concentration by HPLC and convert to SHU using a fixed factor (1 ppm capsaicin = 15 SHU), but the dilution-ratio interpretation is still the most intuitive way to use the scale.

What formula does the calculator use?

It applies conservation of capsaicin: SHU_blend = SHU_hot x V_hot / (V_hot + V_diluent). Rearranged to find diluent volume for a target T: V_diluent = V_hot x (SHU_hot / T - 1). The dilution ratio is V_diluent / V_hot, equivalent to SHU_hot/T - 1.

What counts as a neutral diluent?

Any ingredient with effectively 0 SHU works as a diluent for this model. Common choices are water, vinegar, tomato paste, dairy (milk/cream/yoghurt), coconut milk, honey, or oil. Dairy is especially effective because casein proteins physically bind to capsaicin molecules, accelerating the perceptual drop in heat beyond the pure dilution ratio.

Why does dairy feel more effective than water at the same dilution ratio?

Capsaicin is lipophilic (fat-soluble) and binds to the casein protein in dairy products. This binding prevents capsaicin from re-activating TRPV1 pain receptors in the mouth, giving a perceived relief that exceeds simple concentration dilution. Water, being hydrophilic, does not bind capsaicin and can even spread it around the mouth.

How do I halve the heat of a hot sauce?

To cut the SHU exactly in half, add an equal volume of neutral diluent. For example, 1 tsp of a 40,000 SHU cayenne sauce plus 1 tsp of water gives 20,000 SHU at 2 tsp total. The general rule is that equal parts source and diluent always produce 50% of the original SHU.

Can I dilute a Carolina Reaper (2,200,000 SHU) to jalapeño level (8,000 SHU)?

Yes, though you will need a lot of diluent. The ratio is 2,200,000 / 8,000 - 1 = 274. So 1 tsp of Reaper sauce requires 274 tsp (about 5.7 cups) of diluent to reach jalapeño heat. The calculator gives you the precise figure for any volume and any target.

Scoville Dilution Calculator

Hot sauce recipe getting out of hand? Need to reduce the heat of a chilli paste to a level your guests can enjoy? The Scoville Dilution Calculator tells you exactly how much neutral diluent to add — or shows the resulting heat of any blend — using the same dilution mathematics that underpin the official Scoville Organoleptic Test.

How it works

Capsaicin (and related capsaicinoids) behave like any dissolved substance: their concentration is proportional to the fraction of the total volume they occupy. When you mix a hot ingredient (volume V_h, heat S SHU) with a neutral diluent (volume V_d, heat 0 SHU), the blend heat follows a straightforward conservation rule:

SHU_blend = S x V_h / (V_h + V_d)

Solving for V_d to reach a target T:

V_d = V_h x (S / T - 1)

The dilution ratio (diluent to source) is simply S/T - 1. So to bring a 1,000,000 SHU ghost-pepper mash down to 50,000 SHU, you need S/T - 1 = 19 parts diluent for every 1 part mash — a 19:1 ratio, or 20 times the original volume.

Two modes

Blend calculator — you know both volumes and want to see the resulting SHU. Useful when you are following a recipe and adding a fixed amount of hot sauce to a fixed amount of base.

Target SHU — you know the heat you want and need to find out how much diluent to add. Useful for calibrating a batch of chilli oil, fermented hot sauce, or pepper mash to a reproducible heat specification.

Worked example

You have made a ghost-pepper ferment at roughly 900,000 SHU and want to bottle it as a hot sauce your friends will actually use. Your target heat is around 15,000 SHU (roughly serrano level). You have 50 ml of ferment.

Using the formula:

V_d = 50 x (900,000 / 15,000 - 1) = 50 x 59 = 2,950 ml diluent

The calculator confirms: add approximately 2.95 litres of vinegar/brine to your 50 ml of ferment to produce 3 litres of 15,000 SHU hot sauce. The dilution ratio displayed is 59:1.

Source SHU	Target SHU	Ratio (diluent : source)	Volumes (1 tsp source)
8,000 (jalapeño)	2,500	2.2 : 1	2.2 tsp diluent
40,000 (cayenne)	8,000	4 : 1	4 tsp diluent
200,000 (habanero)	20,000	9 : 1	9 tsp diluent
1,000,000 (ghost)	40,000	24 : 1	24 tsp diluent
2,200,000 (Reaper)	8,000	274 : 1	274 tsp diluent

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