Why are the two directions on such different scales?

Because tinting strength is a property of the pigment, and white and black sit at opposite ends of it. Titanium dioxide white is a scattering pigment: it works by bouncing light back, and to change where a mixture sits you have to add enough of it to compete with everything already there, which means tens of per cent. Carbon black is an absorbing pigment and an extraordinarily efficient one — a small quantity removes light across the whole spectrum, so a fraction of a per cent is a visible move and one per cent is a large one. The practical consequence is that the same number means completely different things in the two directions. Ten per cent of white is an ordinary lightening step. Ten per cent of black is not a dark version of the colour, it is black with a hint of something in it, and the tin is finished. This page gives the two directions different ranges and a different step precisely so that a number that would be harmless one way cannot be typed casually the other way.

Why does adding white mean an extra coat?

Because hiding power comes from the pigment load, and adding white to a tinted paint changes what that load is made of. A factory-tinted colour is a base chosen to carry a particular amount of colourant, and its opacity is a designed property of the finished product. When you add white you are mixing that product with a different one, and the result hides the surface underneath less well than either parent does — the white scatters light but does not block the colour beneath, and the tinted paint is now diluted. On a repaint of a similar colour it may not matter at all. Going over a strong or dark existing colour it matters a great deal, and the symptom is not patchiness you can see coming, it is a third coat you had not planned for and had not bought paint for. The useful rule is that small adjustments are cheap and large ones are not: if you find yourself adding more than a quarter, the honest comparison is against buying the shade you actually want, which will hide better and usually cost less than the paint plus the extra coat.

Can I work out how much lighter it will be?

Not here, and not from any arithmetic you can do without data the paint makers hold. How far a mixture moves depends on the absorption and scattering coefficients of every pigment in both products at every wavelength — that is Kubelka–Munk theory, it is what the tinting machine in the shop is running, and the coefficients are measured per pigment and not published. What makes this worth stating rather than glossing over is that the intuitive shortcut is not merely imprecise but wrong in kind: mixing pigments subtracts light, while averaging two colours on a screen adds it, so the screen answer and the tin answer can differ qualitatively rather than by a few per cent. Add an uncalibrated monitor on top and a predicted swatch is a promise nobody can keep. So the page gives you the thing that is exactly knowable — the volumes, and a ratio you can repeat — and the board gives you the rest. Mixing a sample takes ten minutes and answers the question completely.

Why stir so much before judging it?

Because a tinted mixture reaches uniform appearance well before it reaches uniform composition, and the gap between the two is where the mistakes live. The colourant disperses through the base faster than the base itself circulates, so what looks evenly coloured at the top of the vessel can still be layered further down — particularly in a tall container, and particularly with the small quantities involved in darkening. Judge too early and the mixture looks lighter than it is, you add more, and then the properly stirred result overshoots. The motion matters more than the time: lift material from the bottom and fold it over rather than spinning the surface, which is why a flat paddle beats a spiral one. And run a drill-mounted paddle slowly, because a high-speed vortex drags air into the paint and entrained air shows up as pinholes in the finished film.

Renovation & Construction

Paint Lightening and Darkening Calculator

How much white or tinting black to add for a stated proportion, what the batch becomes, and why lightening and darkening differ so much in scale.

Answers as you typeNo submit button
Every formula citedNamed published standards
Calculated in your browserNo account, nothing uploaded

SettingsSettings for this calculationUS

Market

Imperial · sales tax

Paint to be adjusted

How much of the original paint you are starting from.

Adjust the whole quantity the job needs in one vessel if it will fit. Adjusting two batches separately to the same percentage gets you close, but the two will not be identical, and on a continuous wall the join will show — which is the boxing calculator's subject.

Direction

Adding white, or adding tinting black.

The direction changes the scale of everything below it. Lightening is measured in tens of per cent and darkening in fractions of one, so a percentage that is a sensible lightening step would be a catastrophic darkening one. That asymmetry is the main thing this page exists to make visible.

Tinter added, as a percentage of the base

Per cent of the ORIGINAL paint volume, not of the finished mix.

A fifth added to a batch gives one part tinter to five parts base — so the tinter is a sixth of what comes out rather than a fifth of it. The distinction matters when you scale a recipe up: a proportion of the BASE repeats correctly at any batch size, and a proportion of the total does not.

Sample batch to test first

A small quantity at the same proportion, for a test board.

Especially worth it in the dark direction, where the quantities are small enough that a slip of the wrist is a large proportional error. Zero if you have already tested and are mixing the job.

Tinter to add

0.25 gal

High confidence

0.25 gal of white into 1.25 gal makes 1.50 gal. White is a weak tinter: moving a mid shade visibly takes tens of per cent, and the mixture loses opacity as it goes. Test first: 1.7 fl oz into 8.5 fl oz. How much tinter to add is arithmetic. What colour comes out is not, and nothing here predicts or shows it — no calculator can, without absorption and scattering data measured for the pigments in your particular tin. Adjust the sample first, look at it dry on a board, and commit the batch only after that.

Base paint: 1.25 gal
Finished batch: 1.5 gal
Tinter as a share of the result: 16.67 %
Sample: tinter: 0.01 gal
Usual working range, low: 5 %
Usual working range, high: 50 %

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

The added volume is the stated percentage of the BASE paint, not of the finished batch — so 20 per cent added to 5 L gives 1 L of white and 6 L of paint, and the white is a sixth of what comes out rather than a fifth
The two directions work at completely different scales: white is a weak tinter used in tens of per cent, while tinting black is strong enough to move a shade at a fraction of a per cent. The input ranges here differ by direction for that reason
Adding white REDUCES OPACITY as well as lightening. The mixture hides less well than the paint it came from, which shows up as an extra coat rather than as a colour problem

Inputs used

Paint to be adjusted: 1.25 gal
Direction: Lighten with white
Tinter added, as a percentage of the base: 20
Sample batch to test first: 0.07 gal

Intermediate steps

Base paint: 1.25 gal
Finished batch: 1.5 gal
Tinter as a share of the result: 16.67 %
Sample: tinter: 0.01 gal
Usual working range, low: 5 %
Usual working range, high: 50 %

Final result0.25 gal

Confidence note: 0.25 gal of white into 1.25 gal makes 1.50 gal. White is a weak tinter: moving a mid shade visibly takes tens of per cent, and the mixture loses opacity as it goes. Test first: 1.7 fl oz into 8.5 fl oz. How much tinter to add is arithmetic. What colour comes out is not, and nothing here predicts or shows it — no calculator can, without absorption and scattering data measured for the pigments in your particular tin. Adjust the sample first, look at it dry on a board, and commit the batch only after that.

What this calculation does not cover

How much tinter to add is arithmetic. What colour comes out is not, and nothing here predicts or shows it — no calculator can, without absorption and scattering data measured for the pigments in your particular tin. Adjust the sample first, look at it dry on a board, and commit the batch only after that.
NOTHING HERE IS REVERSIBLE. Tinter added cannot be taken out, and the only correction is more base paint — which you may not have, and which changes the quantity you are working to. Always adjust the small sample first and the batch afterwards, never the other way round.
The percentage is of the BASE, not of the result. Twenty per cent added to five litres gives one litre of tinter and six litres of paint, so the tinter is a sixth of what comes out. Recipes written as a share of the total do not scale the same way, and mixing the two conventions is how a second batch stops matching the first.
WHITE REDUCES OPACITY, and that is the cost nobody budgets for. The mixture hides the surface underneath less well than the paint it was made from, so a wall that would have taken two coats can need three — real material and real labour, on top of the white itself. Where the change is large, a factory-tinted paint at the shade you want will almost always hide better and cost less than the same shade reached by dilution.
Adding white to a paint whose colour comes from a deep or accent base dilutes a heavily loaded product with an unloaded one, which moves durability as well as opacity. It is a normal thing to do in small proportions and a poor way to travel a long way.
Judge the sample dry, at full opacity, on the real substrate and in the room's own light. Almost every paint dries to a different colour from the one it goes on as, a thin test film reads lighter because the board shows through, and a shade chosen under a shop light is a different shade under a north window.
The tinter has to belong to the paint's own system — a white from the same product line, or a tinting black sold for it. Household white gloss stirred into an emulsion, or a universal colourant used past the load its base allows, changes the film rather than only the colour.

Estimated cost — your price

Price per gal ($)

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-15 · v1.0.0

Regulatory standards & verification citations3

The added volume is the stated percentage of the BASE paint, not of the finished batch — so 20 per cent added to 5 L gives 1 L of white and 6 L of paint, and the white is a sixth of what comes out rather than a fifth
The two directions work at completely different scales: white is a weak tinter used in tens of per cent, while tinting black is strong enough to move a shade at a fraction of a per cent. The input ranges here differ by direction for that reason
Adding white REDUCES OPACITY as well as lightening. The mixture hides less well than the paint it came from, which shows up as an extra coat rather than as a colour problem

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Protection this work requires

Stop and check first. Paint under later coats in older housing can be lead-based, and sanding or heat-stripping it produces lead dust that is especially harmful to children and to anyone pregnant. Test before you disturb it — this is a job for a tested, controlled method, not a better mask.

Tools and safety for this job

To roll and cut in two coats and prepare a surface for paint. Generic types, no brands, no prices.

Joint-compound dust is very fine and travels: a P1/FFP1 mask is the minimum, and a damp-sponge finish avoids most of it.
A dust mask does nothing about solvent vapour: ventilate through, and use an organic-vapour (A1) cartridge respirator in an enclosed room.
Most fatal falls on small jobs are from under three metres: use a tower or a ladder tied at the top, and never work off the top two rungs.

Show the 11 tools this job needs

Essential

Brushes
Dust sheets and masking
Filling knife
Roller frame, sleeves and tray
Scraper

Recommended

Caulking gun
Extension pole
Pole sander
Random orbital sander
Step ladder

Optional

Dust extractor or vacuum with a fine filter

Also needed as materials: abrasive discs, caulk and sealant cartridges, masking tape, plastic sheeting, roller sleeves, sanding screens or paper.

what each painting tool is for, and the spec that decides which to buy where one does.

The data behind it: Production rates by operation

How to calculate paint lightening and darkening in 5 steps

Paint to be adjustedHow much of the original paint you are starting from.
DirectionAdding white, or adding tinting black.
Tinter added, as a percentage of the basePer cent of the ORIGINAL paint volume, not of the finished mix.
Sample batch to test firstA small quantity at the same proportion, for a test board.
Tinter to addThe tool computes the tinter to add from those figures and shows the formula, its sources, and a confidence rating alongside it.

Tinter to add by paint to be adjusted

Page defaults, not your figures above.

Paint to be adjusted	Tinter to add (gal)
1 gal	0.2
1.5 gal	0.3
2 gal	0.4
2.5 gal	0.5

Frequently asked questions

Why are the two directions on such different scales?: Because tinting strength is a property of the pigment, and white and black sit at opposite ends of it. Titanium dioxide white is a scattering pigment: it works by bouncing light back, and to change where a mixture sits you have to add enough of it to compete with everything already there, which means tens of per cent. Carbon black is an absorbing pigment and an extraordinarily efficient one — a small quantity removes light across the whole spectrum, so a fraction of a per cent is a visible move and one per cent is a large one. The practical consequence is that the same number means completely different things in the two directions. Ten per cent of white is an ordinary lightening step. Ten per cent of black is not a dark version of the colour, it is black with a hint of something in it, and the tin is finished. This page gives the two directions different ranges and a different step precisely so that a number that would be harmless one way cannot be typed casually the other way.
Why does adding white mean an extra coat?: Because hiding power comes from the pigment load, and adding white to a tinted paint changes what that load is made of. A factory-tinted colour is a base chosen to carry a particular amount of colourant, and its opacity is a designed property of the finished product. When you add white you are mixing that product with a different one, and the result hides the surface underneath less well than either parent does — the white scatters light but does not block the colour beneath, and the tinted paint is now diluted. On a repaint of a similar colour it may not matter at all. Going over a strong or dark existing colour it matters a great deal, and the symptom is not patchiness you can see coming, it is a third coat you had not planned for and had not bought paint for. The useful rule is that small adjustments are cheap and large ones are not: if you find yourself adding more than a quarter, the honest comparison is against buying the shade you actually want, which will hide better and usually cost less than the paint plus the extra coat.
Can I work out how much lighter it will be?: Not here, and not from any arithmetic you can do without data the paint makers hold. How far a mixture moves depends on the absorption and scattering coefficients of every pigment in both products at every wavelength — that is Kubelka–Munk theory, it is what the tinting machine in the shop is running, and the coefficients are measured per pigment and not published. What makes this worth stating rather than glossing over is that the intuitive shortcut is not merely imprecise but wrong in kind: mixing pigments subtracts light, while averaging two colours on a screen adds it, so the screen answer and the tin answer can differ qualitatively rather than by a few per cent. Add an uncalibrated monitor on top and a predicted swatch is a promise nobody can keep. So the page gives you the thing that is exactly knowable — the volumes, and a ratio you can repeat — and the board gives you the rest. Mixing a sample takes ten minutes and answers the question completely.
Why stir so much before judging it?: Because a tinted mixture reaches uniform appearance well before it reaches uniform composition, and the gap between the two is where the mistakes live. The colourant disperses through the base faster than the base itself circulates, so what looks evenly coloured at the top of the vessel can still be layered further down — particularly in a tall container, and particularly with the small quantities involved in darkening. Judge too early and the mixture looks lighter than it is, you add more, and then the properly stirred result overshoots. The motion matters more than the time: lift material from the bottom and fold it over rather than spinning the surface, which is why a flat paddle beats a spiral one. And run a drill-mounted paddle slowly, because a high-speed vortex drags air into the paint and entrained air shows up as pinholes in the finished film.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.