You find a recipe online. Banana bread, looks good, five stars. The ingredients list says 2 cups of flour, 1/3 cup of oil, 3 tablespoons of honey. You have a kitchen scale. No measuring cups. The recipe serves 8 and you need 3 portions for the week. And the temperature says 350F because it is an American blog, but your oven dial shows Celsius.
Three problems in one recipe. None of them are about cooking skill - they are about conversion math that nobody memorizes. A cup of flour weighs 130 g. A cup of honey weighs 350 g. A cup of rolled oats? Just 90 g. The same volume, wildly different weights, because density varies by ingredient.
Why cups and grams never agree
The core issue: volume measures (cups, tablespoons) describe space, not mass. A cup is always 250 ml of space. But how much that space weighs depends entirely on what fills it.
| Ingredient | 1 cup (g) | 1 tbsp (g) | Density (g/ml) |
|---|---|---|---|
| All-purpose flour | 130 | 7.8 | 0.52 |
| White sugar | 200 | 12 | 0.80 |
| Rolled oats | 90 | 5.4 | 0.36 |
| Honey | 350 | 21 | 1.40 |
| Butter (melted) | 225 | 13.5 | 0.90 |
| Vegetable oil | 210 | 12.6 | 0.84 |
| Cocoa powder | 120 | 7.2 | 0.48 |
| Table salt | 250 | 15 | 1.00 |
Flour is fluffy and full of air pockets. Honey is dense liquid. Salt packs tight. This is why "1 cup" without specifying the ingredient tells you almost nothing about weight - and why converting American recipes to grams requires a lookup table for every single line.
The Kitchen Measurement Converter handles both directions: grams to cups (pick the ingredient, get the volume) and volume to volume (cups to tablespoons to ml - pure math, no ingredient needed).
Scaling a recipe without a spreadsheet
Recipe says 4 servings. You need 8. Simple: double everything. But what about 4 to 7? Or 12 to 5? The multiplication factor is 7/4 = 1.75 for the first case and 5/12 = 0.417 for the second. Try doing that in your head for six ingredients while the butter is already softening on the counter.
The Serving Size Calculator takes up to 10 ingredients, applies one factor to all of them, and gives you a side-by-side table. Original vs scaled. No rounding errors, no forgotten lines.
One thing the math cannot solve: eggs. If the factor gives you 2.6 eggs, round to 3. For precise baking, beat the egg, weigh it (one large egg is about 50 g), and measure the fraction.
| Scaling scenario | Factor | 300 g flour becomes | 3 eggs become |
|---|---|---|---|
| 4 to 8 (double) | 2.0x | 600 g | 6 |
| 4 to 1 (single) | 0.25x | 75 g | 0.75 (use 1) |
| 6 to 10 (party) | 1.67x | 500 g | 5 |
| 12 to 5 (halving) | 0.42x | 125 g | 1.25 (use 1) |
| 4 to 7 (odd) | 1.75x | 525 g | 5.25 (use 5) |
The 20-degree rule: fan oven vs conventional
Every fan (convection) oven circulates hot air actively. This makes heat transfer more efficient - roughly equivalent to running 20C hotter than the dial says. The universal adjustment: reduce temperature by 20C and cut time by about 15% compared to a conventional recipe.
Your recipe says 180C conventional? Set your fan oven to 160C. A 35-minute bake becomes 30 minutes. It works the other way too - if the recipe assumes a fan oven and you have conventional, add 20C and 15% more time.
The Baking Time Calculator does three things: calculates meat roasting time from raw weight (8 cuts including chicken, turkey, beef, pork, lamb), adjusts baking temperature and time between fan and conventional ovens, and converts between Celsius, Fahrenheit and Gas Mark.
For meat, the timing formula uses per-500g rates plus a base time. A 1.8 kg chicken at 200C conventional: 20 min per 500g x 3.6 portions + 20 min base = 92 minutes (1 hr 32 min). Fan oven cuts that to 78 minutes at 180C.
Calculate for specific roasting weights
Roasting time for 500 g - single chicken breast or small pork cut Roasting time for 1000 g - small whole chicken or beef joint Roasting time for 1500 g - medium chicken or pork loin Roasting time for 2000 g - large chicken or lamb leg Roasting time for 2500 g - medium turkey or beef roast Roasting time for 3000 g - large beef roast or duck Roasting time for 4000 g - small turkey Roasting time for 5000 g - medium turkey Roasting time for 8000 g - large turkey or holiday roastScale your recipe
Recipe for 1 serving - cooking for yourself Recipe for 2 servings - dinner for two Recipe for 6 servings - family dinner Recipe for 8 servings - small gathering Recipe for 10 servings - dinner party Recipe for 12 servings - larger group Recipe for 20 servings - event or batch cooking Recipe for 50 servings - catering scaleTools discussed in this article
Kitchen Measurement Converter - convert cups, tablespoons, teaspoons to grams and milliliters for 25 common ingredients using accurate density data.
Serving Size Calculator - scale any recipe to a different number of servings. Enter up to 10 ingredients and the calculator adjusts every amount proportionally.
Baking Time Calculator - calculate meat roasting time by weight for 8 cuts, adjust baking temperature between fan and conventional ovens, and convert C/F/Gas Mark.
More cooking tools
These are the first three tools in our cooking category - more converters and calculators are coming soon.